CVE-2026-30872 openwrt CVE debrief

Who should care

Defenders responsible for OpenWrt-based systems, particularly those using versions prior to 24.10.6 and 25.12.1, should assess exposure and prioritize patching. Network administrators and security teams should verify and apply vendor-provided patches, monitor mdns daemon logs for suspicious activity, and consider implementing compensating controls.

Why it matters

CVE-2026-30872 is a critical vulnerability in OpenWrt Project's mdns daemon that can be exploited for remote code execution. Defenders should assess exposure, prioritize patching, and monitor for suspicious activity.

• Remote code execution is potentially enabled
• Buffer overflow vulnerability can be triggered by processing PTR queries
• Patching is required to prevent exploitation

Technical summary

The mdns daemon in OpenWrt Project has a Stack-based Buffer Overflow vulnerability in the match_ipv6_addresses function. This function is triggered when processing PTR queries for IPv6 reverse DNS domains received via multicast DNS on UDP port 5353. The vulnerability allows a remote attacker to potentially enable code execution. The function copies the domain name from name_buffer into a fixed 256-byte stack buffer and then extracts the reverse IPv6 request into a buffer of only 46 bytes. An attacker can supply input larger than 46 bytes, causing an out-of-bounds write. This issue has been fixed in versions 24.10.6 and 25.12.1.

Defensive priority

High

Recommended defensive actions

• Assess exposure and prioritize patching for OpenWrt versions prior to 24.10.6 and 25.12.1
• Verify and apply vendor-provided patches
• Monitor mdns daemon logs for suspicious activity
• Consider implementing compensating controls such as network segmentation or rate limiting
• Review 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 vulnerability is caused by a buffer overflow in the match_ipv6_addresses function. The function copies the domain name from name_buffer into a fixed 256-byte stack buffer and then extracts the reverse IPv6 request into a buffer of only 46 bytes. An attacker can supply input larger than 46 bytes, causing an out-of-bounds write.

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.