#VU56431 NULL pointer dereference in Cisco Systems, Inc products - CVE-2021-34737
Vulnerability identifier: #VU56431
Vulnerability risk: Medium
CVSSv4.0: 4.9 [CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]
CVE-ID:
CWE-ID:
CWE-476
Exploitation vector: Local network
Exploit availability: No
Vulnerable software:
Cisco IOS XR
Operating systems & Components /
Operating system
Cisco IOS XRv 9000 Router
Hardware solutions /
Routers & switches, VoIP, GSM, etc
Cisco ASR 9000 Series Aggregation Services Routers
Hardware solutions /
Routers & switches, VoIP, GSM, etc
NCS5000
Hardware solutions /
Routers & switches, VoIP, GSM, etc
NCS540
Hardware solutions /
Firmware
NCS560
Hardware solutions /
Firmware
NCS5500
Hardware solutions /
Firmware
Vendor: Cisco Systems, Inc
Description
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to a NULL pointer dereference error in the DHCP version 4 (DHCPv4) server feature of Cisco IOS XR Software. A remote non-authenticated attacker can send specially crafted DHCPv4 messages to the affected device, trigger a NULL pointer dereference error and crash the dhcpd process.
Mitigation
Install update from vendor's website.
Vulnerable software versions
Cisco IOS XR: 6.8, 7.0 - 7.0.90, 7.1 - 7.1.25, 7.2.0 - 7.2.12, 7.3 - 7.3.15, 7.4
Cisco IOS XRv 9000 Router: All versions
Cisco ASR 9000 Series Aggregation Services Routers: 7.1 - 7.4
NCS540: All versions
NCS560: All versions
NCS5500: All versions
NCS5000: All versions
External links
https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-dhcp-dos-pjPVReLU
https://bst.cloudapps.cisco.com/bugsearch/bug/CSCvw95930
Q & A
Can this vulnerability be exploited remotely?
Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the local network (LAN).
Is there known malware, which exploits this vulnerability?
No. We are not aware of malware exploiting this vulnerability.
