macsec: fix replay protection at XPN lower-PN wrap

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-63925
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-19 16:17:10 UTC
Updated2026-07-20 15:16:56 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: macsec: fix replay protection at XPN lower-PN wrap In macsec_post_decrypt(), when pn is U32_MAX, pn + 1 overflows u32 to 0 and the first branch never fires. If next_pn_halves.lower is also in the upper half, pn_same_half(pn, lower) is true and the XPN else-if does not fire either, leaving next_pn_halves unchanged. An attacker that captures the legitimate frame carrying pn == 0xFFFFFFFF on an XPN association can then replay it indefinitely, since lowest_pn never rises above the captured pn and macsec_decrypt() reconstructs the same IV. Extend the XPN else-if to also fire when pn + 1 wraps to 0, so receipt of pn == U32_MAX advances next_pn_halves to (upper + 1, 0).

Risk And Classification

Primary CVSS: v3.1 8.1 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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

EPSS: 0.002100000 probability, percentile 0.113670000 (date 2026-07-20)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary8.1HIGHCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
3.1CNADECLARED8.1HIGHCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

CVSS v3.1 Breakdown

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

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected a21ecf0e033807b976967286e6c392f48ee2049f dd7306779c6ce1238f4cdc34f3c1f2246b854457 git Not specified
CNA Linux Linux affected a21ecf0e033807b976967286e6c392f48ee2049f d15130461df388136b62a7b0ce9f66e7e2fa9ff1 git Not specified
CNA Linux Linux affected a21ecf0e033807b976967286e6c392f48ee2049f 23c0e230eab397d7f68be2538790ac41d3bb91fd git Not specified
CNA Linux Linux affected a21ecf0e033807b976967286e6c392f48ee2049f 679e13a65e68a67c8b3c0467c02ee89157ec6f0f git Not specified
CNA Linux Linux affected a21ecf0e033807b976967286e6c392f48ee2049f 79495a1b0944fe31ffd54b54b00211b493590d62 git Not specified
CNA Linux Linux affected a21ecf0e033807b976967286e6c392f48ee2049f 6d00f5c7e5ff7ec4795b7f5f8ed88bd346641652 git Not specified
CNA Linux Linux affected a21ecf0e033807b976967286e6c392f48ee2049f d55acbe577db892b60547b6ef1c020b359331a6d git Not specified
CNA Linux Linux affected a21ecf0e033807b976967286e6c392f48ee2049f e68842b3356471ba56c882209f324613dac47f64 git Not specified
CNA Linux Linux affected 5.7 Not specified
CNA Linux Linux unaffected 5.7 semver Not specified
CNA Linux Linux unaffected 5.10.259 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.210 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.176 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.143 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.93 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.35 6.18.* semver Not specified
CNA Linux Linux unaffected 7.0.12 7.0.* semver Not specified
CNA Linux Linux unaffected 7.1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/79495a1b0944fe31ffd54b54b00211b493590d62 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/23c0e230eab397d7f68be2538790ac41d3bb91fd 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d55acbe577db892b60547b6ef1c020b359331a6d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/6d00f5c7e5ff7ec4795b7f5f8ed88bd346641652 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/e68842b3356471ba56c882209f324613dac47f64 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/679e13a65e68a67c8b3c0467c02ee89157ec6f0f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d15130461df388136b62a7b0ce9f66e7e2fa9ff1 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/dd7306779c6ce1238f4cdc34f3c1f2246b854457 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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