CVE-2023-20135
Description
TOCTOU race condition in Cisco IOS XR Software image verification allows authenticated local attacker to execute arbitrary code.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
TOCTOU race condition in Cisco IOS XR Software image verification allows authenticated local attacker to execute arbitrary code.
Vulnerability
A time-of-check, time-of-use (TOCTOU) race condition exists in the image verification checks of Cisco IOS XR Software when an ISO image is used during an install operation. This vulnerability affects Cisco 8000 Series Routers, NCS 540 Series Routers running NCS540L images, and NCS 5700 Series Routers running NCS5700 images running vulnerable releases of Cisco IOS XR Software [1].
Exploitation
An authenticated, local attacker can exploit this vulnerability by modifying an ISO image and then performing install requests in parallel to trigger the race condition. The attacker must have local access and the ability to initiate install operations [1].
Impact
Successful exploitation allows the attacker to execute arbitrary code on the underlying operating system, potentially gaining full control of the affected device [1].
Mitigation
Cisco has released software updates that address this vulnerability. There are no workarounds. Fixed software versions are specified in Cisco Security Advisory cisco-sa-lnt-L9zOkBz5 [1].
AI Insight generated on May 25, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.
Affected products
2- Range: 7.5.3
Patches
0No patches discovered yet.
Vulnerability mechanics
AI mechanics synthesis has not run for this CVE yet.
References
1News mentions
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