CVE-2026-74657 (GCVE-0-2026-74657)

Vulnerability from cvelistv5 – Published: 2026-08-22 15:32 – Updated: 2026-08-27 12:39
VLAI
Title
ipv4: Fix fib_nlmsg_size() for RTA_VIA nexthops
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv4: Fix fib_nlmsg_size() for RTA_VIA nexthops fib_nlmsg_size() still estimates nexthop space as if every gateway is encoded as an IPv4 RTA_GATEWAY attribute. IPv4 routes can also carry an IPv6 gateway, which fib_nexthop_info() dumps as RTA_VIA. As a result, route notifications can allocate an skb that is too small. fib_dump_info() then fails with -EMSGSIZE and rtmsg_fib() hits the WARN_ON() that marks such failures as a fib_nlmsg_size() bug. With panic_on_warn set, this becomes a kernel panic. Mirror the actual nexthop dump layout in fib_nlmsg_size(): account for IPv6 nexthop gateways dumped as RTA_VIA, for the no-header rtnexthop layout used inside RTA_MULTIPATH, and for RTA_FLOW only when it is actually present.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: d15662682db232da77136cd348f4c9df312ca6f9 , < 57195f0ab5cfbb5ee0864e5aff15ceb48f5a5e28 (git)
Affected: d15662682db232da77136cd348f4c9df312ca6f9 , < 0f0ca602941d0a81ae9514943ca06c55159c6385 (git)
Affected: d15662682db232da77136cd348f4c9df312ca6f9 , < 5307a53599fa762c06e475ee4a375252074fd324 (git)
Affected: d15662682db232da77136cd348f4c9df312ca6f9 , < 7f80ad373ce4a7af5367ff273cea0f16e91387f3 (git)
Affected: d15662682db232da77136cd348f4c9df312ca6f9 , < 4a5dfbae5179f6574695012a980476254df2d295 (git)
Affected: d15662682db232da77136cd348f4c9df312ca6f9 , < a59edda6eda1252340354322d8ab318b2e9052fb (git)
Affected: d15662682db232da77136cd348f4c9df312ca6f9 , < 9b22f13524fa0de0d963bbd3002df6c28bae3395 (git)
Affected: d15662682db232da77136cd348f4c9df312ca6f9 , < 4ff9548d84945d2cbf9e4c207288063a200ea397 (git)
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Linux Linux Affected: 5.2
Unaffected: 0 , < 5.2 (semver)
Unaffected: 5.10.267 , ≤ 5.10.* (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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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: Fix fib_nlmsg_size() for RTA_VIA nexthops\n\nfib_nlmsg_size() still estimates nexthop space as if every gateway is\nencoded as an IPv4 RTA_GATEWAY attribute. IPv4 routes can also carry an\nIPv6 gateway, which fib_nexthop_info() dumps as RTA_VIA.\n\nAs a result, route notifications can allocate an skb that is too small.\nfib_dump_info() then fails with -EMSGSIZE and rtmsg_fib() hits the\nWARN_ON() that marks such failures as a fib_nlmsg_size() bug. With\npanic_on_warn set, this becomes a kernel panic.\n\nMirror the actual nexthop dump layout in fib_nlmsg_size(): account for\nIPv6 nexthop gateways dumped as RTA_VIA, for the no-header rtnexthop\nlayout used inside RTA_MULTIPATH, and for RTA_FLOW only when it is\nactually present."
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-24T11:54:14+00:00",
      "cve": "CVE-2026-74657",
      "id": "CVE-2026-74657",
      "initial_release_date": "2026-08-22T00:00:00+00:00",
      "product_status:known_affected": "198",
      "product_status:known_not_affected": "76",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: ipv4: Fix fib_nlmsg_size() for RTA_VIA nexthops",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74657.json",
      "version": "3"
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}



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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.
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  • 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.


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