odhcpd: pre-auth remote DoS via size_t underflow in dhcpv6_ia_handle_IAs (stack BOF, canary-terminated)

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-53922
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-12 22:17:04 UTC
Updated2026-10-16 20:04:29 UTC
Descriptionodhcpd 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.

Risk And Classification

Primary CVSS: v3.1 6.5 MEDIUM from [email protected]

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

EPSS: 0.003450000 probability, percentile 0.265090000 (date 2026-10-16)

Problem Types: CWE-121 | CWE-191 | CWE-121 CWE-121: Stack-based Buffer Overflow | CWE-191 CWE-191: Integer Underflow (Wrap or Wraparound)

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.5MEDIUMCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED6.5MEDIUMCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Adjacent
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Openwrt Odhcpd affected < c6792bac3905d4bf726d914e9994f6d4b98c5b57 Not specified
CNA Openwrt Openwrt affected < 25.12.5 Not specified

References

ReferenceSourceLinkTags
github.com/openwrt/odhcpd/commit/d08dbcc527cb8f296cd132c1e5bca696e77095b8 [email protected] github.com
github.com/openwrt/odhcpd/commit/c6792bac3905d4bf726d914e9994f6d4b98c5b57 [email protected] github.com
github.com/openwrt/openwrt/releases/tag/v25.12.5 [email protected] github.com
github.com/openwrt/odhcpd/commit/d168c27fb6a55a07ac4c888e09ff2f41e263d7b7 [email protected] github.com
github.com/openwrt/odhcpd/security/advisories/GHSA-7hcw-g2jh-pqv5 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
github.com/openwrt/odhcpd/commit/d329a15413387027453644cd363dca06ade28328 [email protected] github.com
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