CVE-2026-55606 openwrt CVE debrief

Who should care

Defenders responsible for OpenWrt systems using odhcpd should assess exposure and prioritize patching. Network administrators and security teams should monitor for potential exploitation attempts and review network configurations to limit exposure.

Why it matters

The vulnerability in odhcpd can lead to a stack buffer overread, potentially allowing attackers to access sensitive information. Defenders should prioritize patching and monitoring to prevent exploitation.

• Verify and apply patches to prevent potential buffer overread
• Monitor for potential exploitation attempts to detect possible attacks
• Review network configurations to limit exposure and prevent unauthorized access

Technical summary

The odhcpd server is vulnerable to a stack buffer overread attack due to an endianness mismatch when using the DUID length value as the memcmp() size parameter. This can be triggered by a single unauthenticated DHCPv6 packet, resulting in a 2560-byte overread from a 128-byte buffer on little-endian hosts. The vulnerability affects odhcpd versions 25.12 and prior, and defenders should prioritize verifying and applying patches. The issue arises from the DHCPv6 self-loop detection mechanism, which incorrectly uses a network-byte-order DUID length value as the memcmp() size parameter.

Defensive priority

Defenders should prioritize verifying and applying patches for odhcpd versions 25.12 and prior, as well as monitoring for potential exploitation attempts.

Recommended defensive actions

• Verify and apply patches for odhcpd versions 25.12 and prior
• Monitor for potential exploitation attempts
• Review and update network configurations to limit exposure
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The vulnerability is confirmed by the CVE Program record and the OpenWrt advisory. The issue is caused by a mismatch in endianness when using the DUID length value as the memcmp() size parameter. This mismatch leads to a stack buffer overread, potentially allowing attackers to access sensitive information. Defenders should verify and apply patches to prevent potential buffer overread and monitor for potential exploitation attempts to detect possible attacks. The OpenWrt advisory provides additional information on the vulnerability and

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.