FKIE_CVE-2026-99074

Vulnerability from fkie_nvd - Published: 2026-10-23 13:17 - Updated: 2026-10-30 13:21
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv4: stop PMTU walk when nexthop group shrinks Commit 7d3f3b4367f3 ("net: ipv4: Cache pmtu for all packet paths if multipath enabled") made __ip_rt_update_pmtu() update every path. For nexthop objects, fib_info_num_path() and fib_info_nhc() independently load nh->nh_grp. RCU protects each group's lifetime but does not make the loads observe the same group. If replacement shrinks the group after the loop accepts an index, fib_info_nhc() returns NULL and update_or_create_fnhe() dereferences it. A deterministic probe only widened the existing window between the real operations. On v7.2, an RTM_NEWNEXTHOP replacement published a one-member group after the PMTU reader accepted index 1 from a two-member group, producing: KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: update_or_create_fnhe+0x45/0x15b0 Stop when the indexed path is absent. Groups are dense, so no later index exists in that snapshot. The same real-writer window completed 114,423 PMTU iterations without an oops with this check. A reproducer is available on request. Replacement requires CAP_NET_ADMIN in the network namespace. Where unprivileged user namespaces are permitted, a local user can obtain it in a new user and network namespace.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/6619e01855e65ef35723685a557e3eb106f4ecf5
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4a
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/82d83eec893d8ae84f280aec44c60d9fdecc62b5
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/a411df69524f91fe3adb8f9544d33e701fc9732c
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c60d17d6dd61adc761ac6f65a008fefbc54cbf87
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c6d670ac656badfd0e15355e07a13a6bdf3b69fd
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f27483f9975b5065ff67054cc7eb8edac6083488
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/route.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "82d83eec893d8ae84f280aec44c60d9fdecc62b5",
              "status": "affected",
              "version": "fc07a232326a623d0be482e307c08ea7049c2846",
              "versionType": "git"
            },
            {
              "lessThan": "a411df69524f91fe3adb8f9544d33e701fc9732c",
              "status": "affected",
              "version": "b1f7bdee5750d6cbb9497140cd6582abc5fdcb9e",
              "versionType": "git"
            },
            {
              "lessThan": "7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4a",
              "status": "affected",
              "version": "3bed2abab4a682d426624ce9add9d7b6d475d4e4",
              "versionType": "git"
            },
            {
              "lessThan": "c60d17d6dd61adc761ac6f65a008fefbc54cbf87",
              "status": "affected",
              "version": "7f5005457b3072fe1ddf15bfef869f2a1d98e05e",
              "versionType": "git"
            },
            {
              "lessThan": "c6d670ac656badfd0e15355e07a13a6bdf3b69fd",
              "status": "affected",
              "version": "7d3f3b4367f315a61fc615e3138f3d320da8c466",
              "versionType": "git"
            },
            {
              "lessThan": "f27483f9975b5065ff67054cc7eb8edac6083488",
              "status": "affected",
              "version": "7d3f3b4367f315a61fc615e3138f3d320da8c466",
              "versionType": "git"
            },
            {
              "lessThan": "6619e01855e65ef35723685a557e3eb106f4ecf5",
              "status": "affected",
              "version": "7d3f3b4367f315a61fc615e3138f3d320da8c466",
              "versionType": "git"
            },
            {
              "lessThan": "5.15.224",
              "status": "affected",
              "version": "5.15.179",
              "versionType": "semver"
            },
            {
              "lessThan": "6.1.191",
              "status": "affected",
              "version": "6.1.129",
              "versionType": "semver"
            },
            {
              "lessThan": "6.6.160",
              "status": "affected",
              "version": "6.6.79",
              "versionType": "semver"
            },
            {
              "lessThan": "6.12.113",
              "status": "affected",
              "version": "6.12.16",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/ipv4/route.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.13"
            },
            {
              "lessThan": "6.13",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.224",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.191",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.160",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.113",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.57",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.11",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: stop PMTU walk when nexthop group shrinks\n\nCommit 7d3f3b4367f3 (\"net: ipv4: Cache pmtu for all packet paths if\nmultipath enabled\") made __ip_rt_update_pmtu() update every path.\n\nFor nexthop objects, fib_info_num_path() and fib_info_nhc()\nindependently load nh-\u003enh_grp.  RCU protects each group\u0027s lifetime but\ndoes not make the loads observe the same group.  If replacement shrinks\nthe group after the loop accepts an index, fib_info_nhc() returns NULL\nand update_or_create_fnhe() dereferences it.\n\nA deterministic probe only widened the existing window between the real\noperations.  On v7.2, an RTM_NEWNEXTHOP replacement published a\none-member group after the PMTU reader accepted index 1 from a two-member\ngroup, producing:\n\n  KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]\n  RIP: update_or_create_fnhe+0x45/0x15b0\n\nStop when the indexed path is absent.  Groups are dense, so no later\nindex exists in that snapshot.  The same real-writer window completed\n114,423 PMTU iterations without an oops with this check.  A reproducer\nis available on request.\n\nReplacement requires CAP_NET_ADMIN in the network namespace.  Where\nunprivileged user namespaces are permitted, a local user can obtain it\nin a new user and network namespace."
    }
  ],
  "id": "CVE-2026-99074",
  "lastModified": "2026-10-30T13:21:43.640",
  "metrics": {},
  "published": "2026-10-23T13:17:31.397",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6619e01855e65ef35723685a557e3eb106f4ecf5"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4a"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/82d83eec893d8ae84f280aec44c60d9fdecc62b5"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/a411df69524f91fe3adb8f9544d33e701fc9732c"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c60d17d6dd61adc761ac6f65a008fefbc54cbf87"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c6d670ac656badfd0e15355e07a13a6bdf3b69fd"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/f27483f9975b5065ff67054cc7eb8edac6083488"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

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.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON
How durations are calculated

Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.

Loading timeline…




    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.