CVE-2026-53921 | Vulnerability Intelligence

Stored catalog record

Source record retrieved 2026-10-28T10:21:00.938649+00:00. Scheduled imports handle updates; this page does not assert that the provider was queried just now.

Vulnerability overview

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.

Patch review priority

Critical technical severity

CVSS is at least 9.0; exploitation is not established by severity alone.

FIRST EPSS: 1.12% · percentile 66.1 · score date 2026-10-27.

EPSS estimates probability of exploitation in the next 30 days. It does not measure your exposure or prove exploitation. The elevated threshold is 10%; CISA KEV takes precedence. About FIRST EPSS ↗

Severity and scoring

CVSS score: 9.8 · CRITICAL
CVSS version: 3.1
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weaknesses: CWE-121

CVSS measures technical severity; it does not establish whether this vulnerability is being exploited in your environment.

Known exploitation and remediation

Not listed in the CISA catalog retrieved for this record. This does not establish that exploitation has not occurred.

Verify affected versions and patch availability in the vendor advisory before making changes.

Affected products and versions

NVD has not supplied affected-version configurations for this record. Check the vendor references below.

Advisories and references

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