CVE-2023-20135: Cisco IOS XR Software · Improper Verification of Cryptographic Signature
Affects Cisco IOS XR SoftwareSource CVE Database V5
Not known to be exploited · CVSS 5.7 Medium.
Data as of 26 Oct 2026, 10:12 UTC
- EPSS
- 0.09% chance of exploitation in 30 days – higher than 0% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:NExploitation evidence
Disclosed: evidence found.
CVE published 13 Sep 2023
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Cisco Cisco IOS XR Software | Affected
| Fixed in– |
AI-suggested
- Apply Cisco's security patches for IOS XR Software as soon as they become available to address the TOCTOU race condition.
- Restrict local administrative access to IOS XR devices using strong access controls, multi-factor authentication, and network segmentation to limit the attack surface.
- Monitor install operations and ISO image usage on IOS XR devices for unusual or parallel install requests that could indicate exploitation attempts.
- Implement strict change management and image verification policies to prevent unauthorized modification of ISO images.
- Conduct regular audits of privileged accounts and their activities on network devices to detect potential misuse.
- Employ network intrusion detection systems (NIDS) tuned to detect anomalous behavior on IOS XR devices.
- Educate network administrators about the risks of local privilege misuse and the importance of following secure operational procedures.
Description
CVE-2023-20135 is a medium-severity vulnerability in Cisco IOS XR Software that involves improper verification of cryptographic signatures due to a TOCTOU race condition during ISO image installation. An authenticated local attacker with high privileges can exploit this flaw by modifying an ISO image and performing parallel install requests, potentially leading to arbitrary code execution on the device. The vulnerability affects multiple IOS XR versions including 7.5.x through 7.9.x. Exploitation does not require user interaction but does require local authentication and high privileges. No known exploits are currently reported in the wild. This vulnerability poses a significant risk to network infrastructure devices running affected IOS XR versions, especially in environments where local access is possible.