CVE-2026-53920 openwrt CVE debrief

Who should care

Defenders responsible for OpenWrt systems using odhcpd should assess exposure and prioritize patching vulnerable versions. This includes reviewing the system's configuration, monitoring network traffic for suspicious activity, and verifying that odhcpd is properly configured and updated.

Why it matters

CVE-2026-53920 is a high-severity vulnerability in odhcpd that allows for stack memory disclosure, potentially leading to information leaks and increased attack surface.

• Potential disclosure of stack memory contents
• Possible leak of ASLR-useful stack/process contents
• Verification of patch deployment and configuration
• Monitoring for suspicious network activity

Technical summary

The vulnerability occurs when odhcpd's DHCPv6 IA parser accepts an IA_NA or IA_PD option with a body shorter than struct dhcpv6_ia_hdr, casts the option header to that full structure, and reads ia->iaid before proving that the IA body contains the IAID field. If an unauthenticated network-adjacent client places a zero-length or otherwise short IA option at the end of odhcpd's 8192-byte receive stack buffer, the IAID read crosses from data_buf into adjacent stack memory.

Defensive priority

Defenders should prioritize patching vulnerable versions of odhcpd, as this vulnerability allows for stack memory disclosure.

Recommended defensive actions

• Patch vulnerable versions of odhcpd (versions >= 17.01.0, < 25.12.3) to version 25.12.3 or later
• Verify that odhcpd is properly configured and updated
• Monitor network traffic for suspicious activity
• Review compensating controls for exposed systems while remediation is scheduled and verified
• 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
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and source item provide details on the vulnerability, including its description, affected versions, and patch information. The vulnerability occurs when odhcpd's DHCPv6 IA parser accepts an IA_NA or IA_PD option with a body shorter than struct dhcpv6_ia_hdr, casts the option header to that full structure, and reads ia->iaid before proving that the IA body contains the IAID field. If an unauthenticated network-adjacent client places a zero-length or otherwise short IA option at the end of odhcpd's 8192-byte receive stack

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.