Denial of service in Cisco IOS XR DHCP implementation
| Risk | Medium |
| Patch available | YES |
| Number of vulnerabilities | 1 |
| CVE-ID | CVE-2021-34737 |
| CWE-ID | CWE-476 |
| Exploitation vector | Local network |
| Public exploit | N/A |
| 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 |
Security Bulletin
This security bulletin contains one medium risk vulnerability.
1) NULL pointer dereference
EUVDB-ID: #VU56431
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: CVE-2021-34737
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 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.
Install update from vendor's website.
Vulnerable software versionsCisco IOS XR: 6.8 - 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
CPE2.3- cpe:2.3:o:cisco_systems:cisco_ios_xr:6.8:*:*:*:*:*:*:*
- cpe:2.3:o:cisco_systems:cisco_ios_xr:7.0.90:*:*:*:*:*:*:*
- cpe:2.3:o:cisco_systems:cisco_ios_xr:7.1.25:*:*:*:*:*:*:*
- cpe:2.3:o:cisco_systems:cisco_ios_xr:7.2.12:*:*:*:*:*:*:*
- cpe:2.3:o:cisco_systems:cisco_ios_xr:7.3.15:*:*:*:*:*:*:*
- cpe:2.3:o:cisco_systems:cisco_ios_xr:7.4:*:*:*:*:*:*:*
- cpe:2.3:h:cisco_systems:cisco_ios_xrv_9000_router:*:*:*:*:*:*:*:*
- cpe:2.3:h:cisco_systems:cisco_asr_9000_series_aggregation_services_routers:7.1:*:*:*:*:*:*:*
- cpe:2.3:h:cisco_systems:cisco_asr_9000_series_aggregation_services_routers:7.1.1:*:*:*:*:*:*:*
- cpe:2.3:h:cisco_systems:cisco_asr_9000_series_aggregation_services_routers:7.1.2:*:*:*:*:*:*:*
- cpe:2.3:h:cisco_systems:ncs540:*:*:*:*:*:*:*:*
- cpe:2.3:h:cisco_systems:ncs560:*:*:*:*:*:*:*:*
- cpe:2.3:h:cisco_systems:ncs5500:*:*:*:*:*:*:*:*
- cpe:2.3:h:cisco_systems:ncs5000:*:*:*:*:*:*:*:*
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.
