CVE-2026-74659 (GCVE-0-2026-74659)

Vulnerability from cvelistv5 – Published: 2026-08-22 15:32 – Updated: 2026-08-22 15:32
VLAI
Title
net: bridge: mrp: fix uninitialised bytes on the wire
Summary
In the Linux kernel, the following vulnerability has been resolved: net: bridge: mrp: fix uninitialised bytes on the wire br_mrp_alloc_test_skb() builds MRP test frames on an skb from dev_alloc_skb(), which does not clear the linear data area. On the MRA ring-role branch the sub-option TLV header is appended with sub_tlv = skb_put(skb, sizeof(*sub_tlv)); sub_tlv->type = BR_MRP_SUB_TLV_HEADER_TEST_AUTO_MGR; so sub_tlv->length is never written, and the two trailing alignment bytes are appended with a bare skb_put() that does not clear them either. The neighbouring oui and sub_opt regions are explicitly zeroed, so three uninitialised bytes are left in every MRA MRP_Test frame that goes out. Put the sub-option TLV header and the alignment padding in a single skb_put_zero(), which clears both. The AUTO_MGR sub-TLV carries no payload, so the zeroed length field is already the value it should have.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: f7458934b0791c39a001e4d902fc3bf697b439b5 , < 014c062d23c63ec77ef2cf17a0d9363c7441cc94 (git)
Affected: f7458934b0791c39a001e4d902fc3bf697b439b5 , < 7ebc23ff03668042e0b0e4034bb1518d36198d9e (git)
Affected: f7458934b0791c39a001e4d902fc3bf697b439b5 , < 06d58b8d2f053ced82e01efaeb6e7c82891eed58 (git)
Affected: f7458934b0791c39a001e4d902fc3bf697b439b5 , < a5e385eeb2d6dbbbdebfa050e67c34734ae12693 (git)
Affected: f7458934b0791c39a001e4d902fc3bf697b439b5 , < 5912cf1822fbe53ae275c147868740eb384a5d3e (git)
Affected: f7458934b0791c39a001e4d902fc3bf697b439b5 , < e08665218040f8e312abe40f74543186f3c2c941 (git)
Affected: f7458934b0791c39a001e4d902fc3bf697b439b5 , < 63488dba65ef91373ef616575b32eb0eb21459f4 (git)
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Linux Linux Affected: 5.14
Unaffected: 0 , < 5.14 (semver)
Unaffected: 5.15.216 , ≤ 5.15.* (semver)
Unaffected: 6.1.183 , ≤ 6.1.* (semver)
Unaffected: 6.6.152 , ≤ 6.6.* (semver)
Unaffected: 6.12.104 , ≤ 6.12.* (semver)
Unaffected: 6.18.45 , ≤ 6.18.* (semver)
Unaffected: 7.1.9 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
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              "versionType": "semver"
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              "versionType": "semver"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: bridge: mrp: fix uninitialised bytes on the wire\n\nbr_mrp_alloc_test_skb() builds MRP test frames on an skb from\ndev_alloc_skb(), which does not clear the linear data area.  On the MRA\nring-role branch the sub-option TLV header is appended with\n\n\tsub_tlv = skb_put(skb, sizeof(*sub_tlv));\n\tsub_tlv-\u003etype = BR_MRP_SUB_TLV_HEADER_TEST_AUTO_MGR;\n\nso sub_tlv-\u003elength is never written, and the two trailing alignment bytes\nare appended with a bare skb_put() that does not clear them either.  The\nneighbouring oui and sub_opt regions are explicitly zeroed, so three\nuninitialised bytes are left in every MRA MRP_Test frame that goes out.\n\nPut the sub-option TLV header and the alignment padding in a single\nskb_put_zero(), which clears both.  The AUTO_MGR sub-TLV carries no\npayload, so the zeroed length field is already the value it should have."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-22T15:32:32.926Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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        {
          "url": "https://git.kernel.org/stable/c/63488dba65ef91373ef616575b32eb0eb21459f4"
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    "cveId": "CVE-2026-74659",
    "datePublished": "2026-08-22T15:32:32.926Z",
    "dateReserved": "2026-08-15T05:44:03.924Z",
    "dateUpdated": "2026-08-22T15:32:32.926Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
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  "vulnerability-lookup:meta": {
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      "date": "2026-08-29",
      "epss": "0.00173",
      "percentile": "0.06788"
    },
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      "cve": "CVE-2026-74659",
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      "product_status:known_affected": "1",
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      "status": "final",
      "title": "net: bridge: mrp: fix uninitialised bytes on the wire",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-74659.json",
      "version": "2"
    },
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-24T16:24:36+00:00",
      "cve": "CVE-2026-74659",
      "id": "CVE-2026-74659",
      "initial_release_date": "2026-08-22T00:00:00+00:00",
      "product_status:known_not_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net: bridge: mrp: fix uninitialised bytes on the wire",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74659.json",
      "version": "3"
    }
  }
}



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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

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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.