CVE-2026-53922: Stack Overflow (CVSS 6.5)

Description

odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. In commit cfddd56 and earlier, an unauthenticated host on the same link can first obtain two bindings through normal DHCPv6 SOLICIT and REQUEST exchanges and then send a crafted RENEW containing multiple IA_NA options. An earlier matched IA consumes most of the response buffer, an unmatched IA causes the build_ia() status branch to write and return a NOBINDING response larger than the remaining space, and a subsequent matched IA is processed after dhcpv6_ia_handle_IAs() subtracts that over-return from an unsigned size_t. The resulting underflow disables subsequent length checks and permits attacker-controlled IA_ADDR serialization beyond the 512-byte stack buffer pdbuf in handle_client_request(). The stack canary terminates odhcpd, and sustained packets can repeatedly disrupt DHCPv6 service while procd respawns the process. The observed configuration does not establish code execution.

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CVSS v3.1 Score

6.5

MEDIUM

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0035

Probability of exploitation

0.27%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-121 CWE-121

CWE-191 CWE-191

References

Other References

https://github.com/openwrt/odhcpd/commit/c6792bac3905d4bf726d914e9994f6d4b98c5b57 https://github.com/openwrt/odhcpd/commit/d08dbcc527cb8f296cd132c1e5bca696e77095b8 https://github.com/openwrt/odhcpd/commit/d168c27fb6a55a07ac4c888e09ff2f41e263d7b7 https://github.com/openwrt/odhcpd/commit/d329a15413387027453644cd363dca06ade28328 https://github.com/openwrt/odhcpd/security/advisories/GHSA-7hcw-g2jh-pqv5 https://github.com/openwrt/openwrt/releases/tag/v25.12.5 https://github.com/openwrt/odhcpd/security/advisories/GHSA-7hcw-g2jh-pqv5

Frequently Asked Questions

What is CVE-2026-53922? +

odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. In commit cfddd56 and earlier, an unauthenticated host on the same link can first obtain two bindings through normal DHCPv6 SOLICIT and REQUEST exchanges and then send a crafted RENEW containing multiple IA_NA options. An earlier matched IA consumes most of the response buffer, an unmatched IA causes the build_ia() status branch to write and return a NOBINDING response larger than the remaining space, and a subsequent matched IA is processed after dhcpv6_ia_handle_IAs() subtracts that over-return from an unsigned size_t. The resulting underflow disables subsequent length checks and permits attacker-controlled IA_ADDR serialization beyond the 512-byte stack buffer pdbuf in handle_client_request(). The stack canary terminates odhcpd, and sustained packets can repeatedly disrupt DHCPv6 service while procd respawns the process. The observed configuration does not establish code execution. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-53922? +

CVE-2026-53922 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0035, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-53922? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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