CVE-2026-63925 (GCVE-0-2026-63925)

Vulnerability from cvelistv5 – Published: 2026-07-19 14:55 – Updated: 2026-08-05 12:37
VLAI
Title
macsec: fix replay protection at XPN lower-PN wrap
Summary
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).
Severity
8.1 (High)
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: a21ecf0e033807b976967286e6c392f48ee2049f , < dd7306779c6ce1238f4cdc34f3c1f2246b854457 (git)
Affected: a21ecf0e033807b976967286e6c392f48ee2049f , < d15130461df388136b62a7b0ce9f66e7e2fa9ff1 (git)
Affected: a21ecf0e033807b976967286e6c392f48ee2049f , < 23c0e230eab397d7f68be2538790ac41d3bb91fd (git)
Affected: a21ecf0e033807b976967286e6c392f48ee2049f , < 679e13a65e68a67c8b3c0467c02ee89157ec6f0f (git)
Affected: a21ecf0e033807b976967286e6c392f48ee2049f , < 79495a1b0944fe31ffd54b54b00211b493590d62 (git)
Affected: a21ecf0e033807b976967286e6c392f48ee2049f , < 6d00f5c7e5ff7ec4795b7f5f8ed88bd346641652 (git)
Affected: a21ecf0e033807b976967286e6c392f48ee2049f , < d55acbe577db892b60547b6ef1c020b359331a6d (git)
Affected: a21ecf0e033807b976967286e6c392f48ee2049f , < e68842b3356471ba56c882209f324613dac47f64 (git)
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Linux Linux Affected: 5.7
Unaffected: 0 , < 5.7 (semver)
Unaffected: 5.10.259 , ≤ 5.10.* (semver)
Unaffected: 5.15.210 , ≤ 5.15.* (semver)
Unaffected: 6.1.176 , ≤ 6.1.* (semver)
Unaffected: 6.6.143 , ≤ 6.6.* (semver)
Unaffected: 6.12.93 , ≤ 6.12.* (semver)
Unaffected: 6.18.35 , ≤ 6.18.* (semver)
Unaffected: 7.0.12 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmacsec: fix replay protection at XPN lower-PN wrap\n\nIn macsec_post_decrypt(), when pn is U32_MAX, pn + 1 overflows u32 to 0\nand the first branch never fires. If next_pn_halves.lower is also in the\nupper half, pn_same_half(pn, lower) is true and the XPN else-if does not\nfire either, leaving next_pn_halves unchanged. An attacker that captures\nthe legitimate frame carrying pn == 0xFFFFFFFF on an XPN association\ncan then replay it indefinitely, since lowest_pn never rises above\nthe captured pn and macsec_decrypt() reconstructs the same IV.\n\nExtend the XPN else-if to also fire when pn + 1 wraps to 0, so receipt\nof pn == U32_MAX advances next_pn_halves to (upper + 1, 0)."
        }
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              "value": "AV:A - MACsec processes attacker-supplied Ethernet frames via netdev rx_handler on the underlying link; exploitation requires L2 adjacency on the same broadcast domain or point-to-point MACsec link, not remote Internet reachability.\nAC:L - Once XPN with replay protection is deployed, an on-link attacker can passively capture the single legitimate frame at PN 0xFFFFFFFF and then replay it reliably and indefinitely without races or conditions outside their control.\nPR:N - Exploitation requires only the ability to send or replay Ethernet frames on the MACsec link; no local privileges, capabilities, or authentication on the victim Linux host are needed.\nUI:N - Replay injection is fully attacker-driven after capturing the target frame; no victim user or administrator action is required during exploitation.\nS:U - The flaw bypasses MACsec replay protection within the kernel network stack and does not cross a security boundary such as a VM, container, or IOMMU isolation domain.\nC:N - This is a replay-protection logic flaw, not a memory corruption or decryption weakness; the attacker replays already-captured ciphertext and gains no new confidentiality beyond what passive capture already provided.\nI:H - Bypassing replay protection allows unlimited re-injection of previously authenticated payloads into the controlled port, defeating MACsec\u0027s integrity guarantees and enabling repeated delivery of captured control or data traffic on automotive, industrial, and datacenter MACsec links.\nA:H - The commit confirms captured frames can be replayed indefinitely, enabling sustained injection of decrypted traffic that can overwhelm the receiver and deny service to legitimate peers on the protected link."
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    "dateReserved": "2026-07-19T07:54:57.021Z",
    "dateUpdated": "2026-08-05T12:37:20.197Z",
    "state": "PUBLISHED"
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        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmacsec: fix replay protection at XPN lower-PN wrap\n\nIn macsec_post_decrypt(), when pn is U32_MAX, pn + 1 overflows u32 to 0\nand the first branch never fires. If next_pn_halves.lower is also in the\nupper half, pn_same_half(pn, lower) is true and the XPN else-if does not\nfire either, leaving next_pn_halves unchanged. An attacker that captures\nthe legitimate frame carrying pn == 0xFFFFFFFF on an XPN association\ncan then replay it indefinitely, since lowest_pn never rises above\nthe captured pn and macsec_decrypt() reconstructs the same IV.\n\nExtend the XPN else-if to also fire when pn + 1 wraps to 0, so receipt\nof pn == U32_MAX advances next_pn_halves to (upper + 1, 0)."
          }
        ],
        "id": "CVE-2026-63925",
        "lastModified": "2026-07-27T17:44:23.777",
        "metrics": {
          "cvssMetricV31": [
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              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "ADJACENT_NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 8.1,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "NONE",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H",
                "version": "3.1"
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              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        "published": "2026-07-19T16:17:10.787",
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          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Awaiting Analysis"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-05T14:20:54+00:00",
      "cve": "CVE-2026-63925",
      "id": "CVE-2026-63925",
      "initial_release_date": "2026-07-19T00:00:00+00:00",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: macsec: fix replay protection at XPN lower-PN wrap",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63925.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-18T00:46:22Z",
      "cve": "CVE-2026-63925",
      "id": "CVE-2026-63925",
      "initial_release_date": "2026-07-21T13:03:26Z",
      "product_status:known_affected": "586",
      "product_status:known_not_affected": "147",
      "product_status:recommended": "107",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-63925",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-63925.json",
      "version": "10"
    }
  }
}



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Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.