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CVE-2026-63925

HIGHCVSS 8.1/10EPSS 0.34%

Last modified

CVE-2026-63925 is a high-severity vulnerability rated 8.1/10 on the CVSS scale. In 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. EPSS estimates a 0.34% chance of exploitation in the next 30 days.

Description

In 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).

Metrics

CVSS 3.1
8.1/10

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

EPSS Probability
0.34%

26.6th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= a21ecf0e033807b976967286e6c392f48ee2049f, < dd7306779c6ce1238f4cdc34f3c1f2246b854457; >= a21ecf0e033807b976967286e6c392f48ee2049f, < d15130461df388136b62a7b0ce9f66e7e2fa9ff1; >= a21ecf0e033807b976967286e6c392f48ee2049f, < 23c0e230eab397d7f68be2538790ac41d3bb91fd; >= a21ecf0e033807b976967286e6c392f48ee2049f, < 679e13a65e68a67c8b3c0467c02ee89157ec6f0f; >= a21ecf0e033807b976967286e6c392f48ee2049f, < 79495a1b0944fe31ffd54b54b00211b493590d62; >= a21ecf0e033807b976967286e6c392f48ee2049f, < 6d00f5c7e5ff7ec4795b7f5f8ed88bd346641652; >= a21ecf0e033807b976967286e6c392f48ee2049f, < d55acbe577db892b60547b6ef1c020b359331a6d; >= a21ecf0e033807b976967286e6c392f48ee2049f, < e68842b3356471ba56c882209f324613dac47f64
LinuxLinux5.7

References

Timeline

Published
Last Modified
Status
Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-63925?
In 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).
How severe is CVE-2026-63925?
CVE-2026-63925 has a CVSS score of 8.1/10 (HIGH severity). The EPSS model estimates a 0.34% probability of exploitation in the next 30 days.
How do I fix CVE-2026-63925?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST