Critical 9.8Published Oct 23, 2026

CVE-2026-53921odhcpd: Stack buffer overflow in DHCPv6 IA reply serialization (2 independent sites)

Updated under an hour ago (Oct 28, 2026, 10:40 AM ET)

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It affects openwrt odhcpd. Add what you run to find out whether that includes you.

EPSS puts the chance of exploitation in the next 30 days at 1.12%, higher than 66% of scored CVEs.

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Every CVE for openwrt odhcpd

Exploited in the last 30 days

odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. Prior to version 25.12, odhcpd's DHCPv6 IA response handler writes past the end of a fixed 512-byte stack buffer (pdbuf) when a single DHCPv6 REQUEST carries enough IA options to nearly exhaust the reply space. Two independent overflow sites exist in the same call chain, both reachable from the network via a single unauthenticated UDP packet. odhcpd runs as root on OpenWrt; embedded targets often lack stack canaries and ASLR, making code execution realistic. This issue has been patched in version 25.12.

CVSS: 9.8 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-121
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): 1.12% (percentile 66)
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Oct 23, 2026
First seen by InfoSec Signals: Oct 23, 2026

Affected products

Affected products

openwrt odhcpd openwrt:odhcpd (from the name)	before 25.12	CNA record

References

References

https://github.com/openwrt/odhcpd/security/advisories/GHSA-7fwx-hhrg-3496	x-refsource-confirm
https://github.com/openwrt/odhcpd/commit/0320032ae313452f3c8cb8725c621dd06c36dc03	x-refsource-misc
https://github.com/openwrt/odhcpd/commit/03dacc23356b5789842b9d1bba0200fd005e35f3	x-refsource-misc
https://github.com/openwrt/odhcpd/commit/2a42d34c3615e2449ca273f673eee7c429d819a9	x-refsource-misc
https://github.com/openwrt/odhcpd/commit/6634b7a3c79c41a27687925c98c35c8aea2f2b5a	x-refsource-misc
https://github.com/openwrt/odhcpd/commit/d168c27fb6a55a07ac4c888e09ff2f41e263d7b7	x-refsource-misc
https://github.com/openwrt/odhcpd/commit/d329a15413387027453644cd363dca06ade28328	x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.