Cisco IOS XR and Cisco NX-OS Software IPv6 Access Control List Bypass Vulnerability
Priority LOW 37CWE-284Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- No fix listed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-284.
Summary
A vulnerability in the IPv6 traffic processing of Cisco IOS XR Software and Cisco NX-OS Software for certain Cisco devices could allow an unauthenticated, remote attacker to bypass an IPv6 access control list (ACL) that is configured for an interface of an affected device. The vulnerability is due to improper processing of IPv6 traffic that is sent through an affected device. An attacker could exploit this vulnerability by sending crafted IPv6 packets that traverse the affected device. A successful exploit could allow the attacker to access resources that would typically be protected by the interface ACL.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.01237 69th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Cisco | Cisco IOS XR Software | all versions | — | No fix listed | CNA |
- Cisco IOS XR Software VendorCisco Affected all versions Fixed in — No fix listed CNA
CPE configurations NVD · 14
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:cisco:ios_xr:*:*:*:*:*:*:*:* | before 6.6.3 | Vulnerable | Cisco |
| cpe:2.3:o:cisco:ios_xr:7.1.0:*:*:*:*:*:*:* | 7.1.0 | Vulnerable | Cisco |
| cpe:2.3:o:cisco:ios_xr:7.2.0:*:*:*:*:*:*:* | 7.2.0 | Vulnerable | Cisco |
| cpe:2.3:h:cisco:ncs_540:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:ncs_5501:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:ncs_5501-se:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:ncs_5502:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:ncs_5502-se:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:ncs_5508:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:ncs_5516:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
- cpe:2.3:o:cisco:ios_xr:*:*:*:*:*:*:*:* Versions before 6.6.3 Vulnerable ·Cisco
- cpe:2.3:o:cisco:ios_xr:7.1.0:*:*:*:*:*:*:* Versions 7.1.0 Vulnerable ·Cisco
- cpe:2.3:o:cisco:ios_xr:7.2.0:*:*:*:*:*:*:* Versions 7.2.0 Vulnerable ·Cisco
- cpe:2.3:h:cisco:ncs_540:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:ncs_5501:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:ncs_5501-se:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:ncs_5502:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:ncs_5502-se:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:ncs_5508:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:ncs_5516:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
Show 4 more CPE
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:h:cisco:ncs_560:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:o:cisco:nx-os:-:*:*:*:*:*:*:* | not specified by NVD | Vulnerable | Cisco |
| cpe:2.3:h:cisco:nexus_3600:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_9500_r:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
- cpe:2.3:h:cisco:ncs_560:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:o:cisco:nx-os:-:*:*:*:*:*:*:* Versions not specified by NVD Vulnerable ·Cisco
- cpe:2.3:h:cisco:nexus_3600:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_9500_r:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
Remediation
No fixed version listed by the sources yet.
Timeline
- 2026-10-02 Threatist record created from CVE-2021-1389
- 2026-10-03 Alias added: GHSA-r95g-ccc3-r2m4
References
More Cisco Ios Xr vulnerabilities
- TI-2020-02680 Cisco IOS XR Software Cisco Discovery Protocol Format String Vulnerability KEVCVSS 3.1HIGH 8.8
- TI-2018-00135 Memory corruption in Cisco IOS, IOS XE, and IOS XR KEVCVSS 3.1HIGH 8.8
- TI-2020-03113 Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerabilities KEVCVSS 3.1HIGH 8.6
- TI-2020-03110 Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability KEVCVSS 3.1HIGH 8.6
- TI-2018-00142 Memory corruption in Cisco IOS, IOS XE, and IOS XR KEVCVSS 3.1HIGH 8.0
- TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
Sources
- CVE-2021-1389 · CVE Program
- CVE-2021-1389 · NVD
- FIRST EPSS
- GHSA-r95g-ccc3-r2m4 · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences