Quick answers
- Is CVE-2026-53921 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-53921 being exploited in the wild.
- How severe is CVE-2026-53921?
- Critical severity, with a CVSS score of 9.8, published 23 October 2026.
- Which products and versions are affected?
- OpenWrt Odhcpd before 25.12.
- Is there a fix for CVE-2026-53921?
- Yes: fixed in 25.12. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-53921 attacked?
- It is attacked over the network, in a network appliance.
- Am I affected by CVE-2026-53921?
- Check whether you run OpenWrt Odhcpd at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: 25.12
Technical details
The vulnerability exists in the dhcpv6_ia_handle_IAs function where a single DHCPv6 REQUEST packet carrying multiple IA options can overflow a fixed 512-byte pdbuf stack buffer. Two independent out-of-bounds write sites exist in the same call chain, both reachable via unauthenticated network UDP traffic. The defect was initially in the buffer length check logic, then compounded by an incorrect write offset for the DHCPv6 Reconfigure Accept authentication option.
Affected products
- OpenWrt odhcpd before 25.12
Timeline
- 2026-10-23: disclosed
- 2026-10-23: patched