rxrpc: Fix missing validation of ticket length in non-XDR key preparsing

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Summary

CVECVE-2026-31696
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-01 14:16:19 UTC
Updated2026-05-06 19:17:41 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix missing validation of ticket length in non-XDR key preparsing In rxrpc_preparse(), there are two paths for parsing key payloads: the XDR path (for large payloads) and the non-XDR path (for payloads <= 28 bytes). While the XDR path (rxrpc_preparse_xdr_rxkad()) correctly validates the ticket length against AFSTOKEN_RK_TIX_MAX, the non-XDR path fails to do so. This allows an unprivileged user to provide a very large ticket length. When this key is later read via rxrpc_read(), the total token size (toksize) calculation results in a value that exceeds AFSTOKEN_LENGTH_MAX, triggering a WARN_ON(). [ 2001.302904] WARNING: CPU: 2 PID: 2108 at net/rxrpc/key.c:778 rxrpc_read+0x109/0x5c0 [rxrpc] Fix this by adding a check in the non-XDR parsing path of rxrpc_preparse() to ensure the ticket length does not exceed AFSTOKEN_RK_TIX_MAX, bringing it into parity with the XDR parsing logic.

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from [email protected]

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

EPSS: 0.000210000 probability, percentile 0.057670000 (date 2026-05-05)

Problem Types: CWE-787

CVSS v3.1 Breakdown

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

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247 1fa36cf495b0023e8475d038535c05e4063211e1 git Not specified
CNA Linux Linux affected 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247 4458757c020592a3094366e0fb20457383b42f92 git Not specified
CNA Linux Linux affected 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247 ce383ba615339f8eaec646a166d2c2b015bb5ca0 git Not specified
CNA Linux Linux affected 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247 a1be1c9ece26cea69654f28b255ff9a7906b897b git Not specified
CNA Linux Linux affected 8a7a3eb4ddbe7c7e639170a64adede7cbd5a9247 ac33733b10b484d666f97688561670afd5861383 git Not specified
CNA Linux Linux affected 3.17 Not specified
CNA Linux Linux unaffected 3.17 semver Not specified
CNA Linux Linux unaffected 6.6.136 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.84 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.25 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.2 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/4458757c020592a3094366e0fb20457383b42f92 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/ce383ba615339f8eaec646a166d2c2b015bb5ca0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/1fa36cf495b0023e8475d038535c05e4063211e1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/a1be1c9ece26cea69654f28b255ff9a7906b897b 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/ac33733b10b484d666f97688561670afd5861383 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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