Debian update for xen
| Risk | Medium |
| Patch available | YES |
| Number of vulnerabilities | 11 |
| CVE-ID | CVE-2020-29479 CVE-2020-29480 CVE-2020-29481 CVE-2020-29482 CVE-2020-29483 CVE-2020-29484 CVE-2020-29485 CVE-2020-29486 CVE-2020-29566 CVE-2020-29570 CVE-2020-29571 |
| CWE-ID | CWE-732 CWE-20 CWE-426 CWE-416 CWE-476 CWE-401 CWE-770 CWE-674 |
| Exploitation vector | Network |
| Public exploit | N/A |
| Vulnerable software Subscribe |
Debian Linux Operating systems & Components / Operating system xen (Debian package) Operating systems & Components / Operating system package or component |
| Vendor | Debian |
Security Bulletin
This security bulletin contains information about 11 vulnerabilities.
1) Incorrect permission assignment for critical resource
EUVDB-ID: #VU49129
Risk: Low
CVSSv3.1: 7.7 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C]
CVE-ID: CVE-2020-29479
CWE-ID:
CWE-732 - Incorrect Permission Assignment for Critical Resource
Exploit availability: No
DescriptionThe vulnerability allows a local authenticated user to execute arbitrary code.
An issue was discovered in Xen through 4.14.x. In the Ocaml xenstored implementation, the internal representation of the tree has special cases for the root node, because this node has no parent. Unfortunately, permissions were not checked for certain operations on the root node. Unprivileged guests can get and modify permissions, list, and delete the root node. (Deleting the whole xenstore tree is a host-wide denial of service.) Achieving xenstore write access is also possible. All systems using oxenstored are vulnerable. Building and using oxenstored is the default in the upstream Xen distribution, if the Ocaml compiler is available. Systems using C xenstored are not vulnerable.
MitigationUpdate xen package to version 4.11.4+57-g41a822c392-2.
Vulnerable software versionsDebian Linux: All versions
xen (Debian package): before 4.11.4+57-g41a822c392-2
CPE2.3 External linkshttp://www.debian.org/security/2020/dsa-4812
Q & A
Can this vulnerability be exploited remotely?
No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.
Is there known malware, which exploits this vulnerability?
No. We are not aware of malware exploiting this vulnerability.
2) Input validation error
EUVDB-ID: #VU49130
Risk: Low
CVSSv3.1: 2 [CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:N/E:U/RL:O/RC:C]
CVE-ID: CVE-2020-29480
CWE-ID:
CWE-20 - Improper input validation
Exploit availability: No
DescriptionThe vulnerability allows a local privileged user to gain access to sensitive information.
An issue was discovered in Xen through 4.14.x. Neither xenstore implementation does any permission checks when reporting a xenstore watch event. A guest administrator can watch the root xenstored node, which will cause notifications for every created, modified, and deleted key. A guest administrator can also use the special watches, which will cause a notification every time a domain is created and destroyed. Data may include: number, type, and domids of other VMs; existence and domids of driver domains; numbers of virtual interfaces, block devices, vcpus; existence of virtual framebuffers and their backend style (e.g., existence of VNC service); Xen VM UUIDs for other domains; timing information about domain creation and device setup; and some hints at the backend provisioning of VMs and their devices. The watch events do not contain values stored in xenstore, only key names. A guest administrator can observe non-sensitive domain and device lifecycle events relating to other guests. This information allows some insight into overall system configuration (including the number and general nature of other guests), and configuration of other guests (including the number and general nature of other guests' devices). This information might be commercially interesting or might make other attacks easier. There is not believed to be exposure of sensitive data. Specifically, there is no exposure of VNC passwords, port numbers, pathnames in host and guest filesystems, cryptographic keys, or within-guest data.
MitigationUpdate xen package to version 4.11.4+57-g41a822c392-2.
Vulnerable software versionsDebian Linux: All versions
xen (Debian package): before 4.11.4+57-g41a822c392-2
CPE2.3 External linkshttp://www.debian.org/security/2020/dsa-4812
Q & A
Can this vulnerability be exploited remotely?
No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.
Is there known malware, which exploits this vulnerability?
No. We are not aware of malware exploiting this vulnerability.
3) Input validation error
EUVDB-ID: #VU49131
Risk: Low
CVSSv3.1: 7.7 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C]
CVE-ID: CVE-2020-29481
CWE-ID:
CWE-20 - Improper input validation
Exploit availability: No
DescriptionThe vulnerability allows a local authenticated user to execute arbitrary code.
An issue was discovered in Xen through 4.14.x. Access rights of Xenstore nodes are per domid. Unfortunately, existing granted access rights are not removed when a domain is being destroyed. This means that a new domain created with the same domid will inherit the access rights to Xenstore nodes from the previous domain(s) with the same domid. Because all Xenstore entries of a guest below /local/domain/<domid> are being deleted by Xen tools when a guest is destroyed, only Xenstore entries of other guests still running are affected. For example, a newly created guest domain might be able to read sensitive information that had belonged to a previously existing guest domain. Both Xenstore implementations (C and Ocaml) are vulnerable.
MitigationUpdate xen package to version 4.11.4+57-g41a822c392-2.
Vulnerable software versionsDebian Linux: All versions
xen (Debian package): before 4.11.4+57-g41a822c392-2
CPE2.3 External linkshttp://www.debian.org/security/2020/dsa-4812
Q & A
Can this vulnerability be exploited remotely?
No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.
Is there known malware, which exploits this vulnerability?
No. We are not aware of malware exploiting this vulnerability.
4) Untrusted search path
EUVDB-ID: #VU49132
Risk: Low
CVSSv3.1: 5.2 [CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:H/E:U/RL:O/RC:C]
CVE-ID: CVE-2020-29482
CWE-ID:
CWE-426 - Untrusted Search Path
Exploit availability: No
DescriptionThe vulnerability allows a local privileged user to a crash the entire system.
An issue was discovered in Xen through 4.14.x. A guest may access xenstore paths via absolute paths containing a full pathname, or via a relative path, which implicitly includes /local/domain/$DOMID for their own domain id. Management tools must access paths in guests' namespaces, necessarily using absolute paths. oxenstored imposes a pathname limit that is applied solely to the relative or absolute path specified by the client. Therefore, a guest can create paths in its own namespace which are too long for management tools to access. Depending on the toolstack in use, a malicious guest administrator might cause some management tools and debugging operations to fail. For example, a guest administrator can cause "xenstore-ls -r" to fail. However, a guest administrator cannot prevent the host administrator from tearing down the domain. All systems using oxenstored are vulnerable. Building and using oxenstored is the default in the upstream Xen distribution, if the Ocaml compiler is available. Systems using C xenstored are not vulnerable.
MitigationUpdate xen package to version 4.11.4+57-g41a822c392-2.
Vulnerable software versionsDebian Linux: All versions
xen (Debian package): before 4.11.4+57-g41a822c392-2
CPE2.3 External linkshttp://www.debian.org/security/2020/dsa-4812
Q & A
Can this vulnerability be exploited remotely?
No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.
Is there known malware, which exploits this vulnerability?
No. We are not aware of malware exploiting this vulnerability.
5) Use-after-free
EUVDB-ID: #VU49133
Risk: Low
CVSSv3.1: 5.7 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H/E:U/RL:O/RC:C]
CVE-ID: CVE-2020-29483
CWE-ID:
CWE-416 - Use After Free
Exploit availability: No
DescriptionThe vulnerability allows a local authenticated user to a crash the entire system.
An issue was discovered in Xen through 4.14.x. Xenstored and guests communicate via a shared memory page using a specific protocol. When a guest violates this protocol, xenstored will drop the connection to that guest. Unfortunately, this is done by just removing the guest from xenstored's internal management, resulting in the same actions as if the guest had been destroyed, including sending an @releaseDomain event. @releaseDomain events do not say that the guest has been removed. All watchers of this event must look at the states of all guests to find the guest that has been removed. When an @releaseDomain is generated due to a domain xenstored protocol violation, because the guest is still running, the watchers will not react. Later, when the guest is actually destroyed, xenstored will no longer have it stored in its internal data base, so no further @releaseDomain event will be sent. This can lead to a zombie domain; memory mappings of that guest's memory will not be removed, due to the missing event. This zombie domain will be cleaned up only after another domain is destroyed, as that will trigger another @releaseDomain event. If the device model of the guest that violated the Xenstore protocol is running in a stub-domain, a use-after-free case could happen in xenstored, after having removed the guest from its internal data base, possibly resulting in a crash of xenstored. A malicious guest can block resources of the host for a period after its own death. Guests with a stub domain device model can eventually crash xenstored, resulting in a more serious denial of service (the prevention of any further domain management operations). Only the C variant of Xenstore is affected; the Ocaml variant is not affected. Only HVM guests with a stubdom device model can cause a serious DoS.
MitigationUpdate xen package to version 4.11.4+57-g41a822c392-2.
Vulnerable software versionsDebian Linux: All versions
xen (Debian package): before 4.11.4+57-g41a822c392-2
CPE2.3 External linkshttp://www.debian.org/security/2020/dsa-4812
Q & A
Can this vulnerability be exploited remotely?
No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.
Is there known malware, which exploits this vulnerability?
No. We are not aware of malware exploiting this vulnerability.
6) NULL pointer dereference
EUVDB-ID: #VU49134
Risk: Medium
CVSSv3.1: 5.2 [AV:L/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:H/E:U/RL:O/RC:C]
CVE-ID: CVE-2020-29484
CWE-ID:
CWE-476 - NULL Pointer Dereference
Exploit availability: No
DescriptionThe vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to a NULL pointer dereference error. A remote attacker can trigger denial of service conditions via Xenstore messages, consisting of a message header and the payload. The payload length is limited to 4096 bytes. Any request to xenstored resulting in a response with a payload longer than 4096 bytes will result in an error. When registering a watch, the payload length limit applies to the combined length of the watched path and the specified tag. Because watches for a specific path are also triggered for all nodes below that path, the payload of a watch event message can be longer than the payload needed to register the watch. A malicious guest that registers a watch using a very large tag (i.e., with a registration operation payload length close to the 4096 byte limit) can cause the generation of watch events with a payload length larger than 4096 bytes, by writing to Xenstore entries below the watched path. This will result in an error condition in xenstored. This error can result in a NULL pointer dereference, leading to a crash of xenstored. A malicious guest administrator can cause xenstored to crash, leading to a denial of service. Following a xenstored crash, domains may continue to run, but management operations will be impossible. Only C xenstored is affected, oxenstored is not affected.
MitigationUpdate xen package to version 4.11.4+57-g41a822c392-2.
Vulnerable software versionsDebian Linux: All versions
xen (Debian package): before 4.11.4+57-g41a822c392-2
CPE2.3 External linkshttp://www.debian.org/security/2020/dsa-4812
Q & A
Can this vulnerability be exploited remotely?
No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.
Is there known malware, which exploits this vulnerability?
No. We are not aware of malware exploiting this vulnerability.
7) Memory leak
EUVDB-ID: #VU49135
Risk: Low
CVSSv3.1: 4.8 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C]
CVE-ID: CVE-2020-29485
CWE-ID:
CWE-401 - Missing release of memory after effective lifetime
Exploit availability: No
DescriptionThe vulnerability allows a local authenticated user to perform a denial of service (DoS) attack.
An issue was discovered in Xen 4.6 through 4.14.x. When acting upon a guest XS_RESET_WATCHES request, not all tracking information is freed. A guest can cause unbounded memory usage in oxenstored. This can lead to a system-wide DoS. Only systems using the Ocaml Xenstored implementation are vulnerable. Systems using the C Xenstored implementation are not vulnerable.
MitigationUpdate xen package to version 4.11.4+57-g41a822c392-2.
Vulnerable software versionsDebian Linux: All versions
xen (Debian package): before 4.11.4+57-g41a822c392-2
CPE2.3 External linkshttp://www.debian.org/security/2020/dsa-4812
Q & A
Can this vulnerability be exploited remotely?
No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.
Is there known malware, which exploits this vulnerability?
No. We are not aware of malware exploiting this vulnerability.
8) Allocation of Resources Without Limits or Throttling
EUVDB-ID: #VU49136
Risk: Low
CVSSv3.1: 5.2 [CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:H/E:U/RL:O/RC:C]
CVE-ID: CVE-2020-29486
CWE-ID:
CWE-770 - Allocation of Resources Without Limits or Throttling
Exploit availability: No
DescriptionThe vulnerability allows a local privileged user to a crash the entire system.
An issue was discovered in Xen through 4.14.x. Nodes in xenstore have an ownership. In oxenstored, a owner could give a node away. However, node ownership has quota implications. Any guest can run another guest out of quota, or create an unbounded number of nodes owned by dom0, thus running xenstored out of memory A malicious guest administrator can cause a denial of service against a specific guest or against the whole host. All systems using oxenstored are vulnerable. Building and using oxenstored is the default in the upstream Xen distribution, if the Ocaml compiler is available. Systems using C xenstored are not vulnerable.
MitigationUpdate xen package to version 4.11.4+57-g41a822c392-2.
Vulnerable software versionsDebian Linux: All versions
xen (Debian package): before 4.11.4+57-g41a822c392-2
CPE2.3 External linkshttp://www.debian.org/security/2020/dsa-4812
Q & A
Can this vulnerability be exploited remotely?
No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.
Is there known malware, which exploits this vulnerability?
No. We are not aware of malware exploiting this vulnerability.
9) Uncontrolled Recursion
EUVDB-ID: #VU49137
Risk: Low
CVSSv3.1: 4.8 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C]
CVE-ID: CVE-2020-29566
CWE-ID:
CWE-674 - Uncontrolled Recursion
Exploit availability: No
DescriptionThe vulnerability allows a local authenticated user to perform a denial of service (DoS) attack.
An issue was discovered in Xen through 4.14.x. When they require assistance from the device model, x86 HVM guests must be temporarily de-scheduled. The device model will signal Xen when it has completed its operation, via an event channel, so that the relevant vCPU is rescheduled. If the device model were to signal Xen without having actually completed the operation, the de-schedule / re-schedule cycle would repeat. If, in addition, Xen is resignalled very quickly, the re-schedule may occur before the de-schedule was fully complete, triggering a shortcut. This potentially repeating process uses ordinary recursive function calls, and thus could result in a stack overflow. A malicious or buggy stubdomain serving a HVM guest can cause Xen to crash, resulting in a Denial of Service (DoS) to the entire host. Only x86 systems are affected. Arm systems are not affected. Only x86 stubdomains serving HVM guests can exploit the vulnerability.
MitigationUpdate xen package to version 4.11.4+57-g41a822c392-2.
Vulnerable software versionsDebian Linux: All versions
xen (Debian package): before 4.11.4+57-g41a822c392-2
CPE2.3 External linkshttp://www.debian.org/security/2020/dsa-4812
Q & A
Can this vulnerability be exploited remotely?
No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.
Is there known malware, which exploits this vulnerability?
No. We are not aware of malware exploiting this vulnerability.
10) Allocation of Resources Without Limits or Throttling
EUVDB-ID: #VU49139
Risk: Medium
CVSSv3.1: 5.7 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C]
CVE-ID: CVE-2020-29570
CWE-ID:
CWE-770 - Allocation of Resources Without Limits or Throttling
Exploit availability: No
DescriptionThe vulnerability allows a remote non-authenticated attacker to perform a denial of service (DoS) attack.
An issue was discovered in Xen through 4.14.x. Recording of the per-vCPU control block mapping maintained by Xen and that of pointers into the control block is reversed. The consumer assumes, seeing the former initialized, that the latter are also ready for use. Malicious or buggy guest kernels can mount a Denial of Service (DoS) attack affecting the entire system.
MitigationUpdate xen package to version 4.11.4+57-g41a822c392-2.
Vulnerable software versionsDebian Linux: All versions
xen (Debian package): before 4.11.4+57-g41a822c392-2
CPE2.3 External linkshttp://www.debian.org/security/2020/dsa-4812
Q & A
Can this vulnerability be exploited remotely?
Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.
Is there known malware, which exploits this vulnerability?
No. We are not aware of malware exploiting this vulnerability.
11) NULL pointer dereference
EUVDB-ID: #VU49140
Risk: Medium
CVSSv3.1: 5.7 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C]
CVE-ID: CVE-2020-29571
CWE-ID:
CWE-476 - NULL Pointer Dereference
Exploit availability: No
DescriptionThe vulnerability allows a remote non-authenticated attacker to perform a denial of service (DoS) attack.
An issue was discovered in Xen through 4.14.x. A bounds check common to most operation time functions specific to FIFO event channels depends on the CPU observing consistent state. While the producer side uses appropriately ordered writes, the consumer side isn't protected against re-ordered reads, and may hence end up de-referencing a NULL pointer. Malicious or buggy guest kernels can mount a Denial of Service (DoS) attack affecting the entire system. Only Arm systems may be vulnerable. Whether a system is vulnerable depends on the specific CPU. x86 systems are not vulnerable.
MitigationUpdate xen package to version 4.11.4+57-g41a822c392-2.
Vulnerable software versionsDebian Linux: All versions
xen (Debian package): before 4.11.4+57-g41a822c392-2
CPE2.3 External linkshttp://www.debian.org/security/2020/dsa-4812
Q & A
Can this vulnerability be exploited remotely?
Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.
Is there known malware, which exploits this vulnerability?
No. We are not aware of malware exploiting this vulnerability.
