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CVE-2026-99074

ipv4: stop PMTU walk when nexthop group shrinks

Products / packages Linux

Published

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Severity and exploitation

Not in CISA KEVNo CVSS score

KEV coverage does not rule out exploitation.

KEV checked 14/11/2026, 21:10:34 UTC

Severity

unknown

CVSS measures technical severity, not the likelihood of an attack.

Known exploitation

Not listed in the checked CISA KEV catalog

Absence from CISA KEV does not rule out attacks.

Public exploit

Not established by this record

Missing evidence does not mean no public exploit exists.

Remediation

Fix status not established

No structured fix or guidance is available here. Check the latest publisher advisory.

What this means

The Linux kernel has a vulnerability where the PMTU walk does not stop when the nexthop group shrinks, potentially causing a null pointer dereference. This affects Linux kernel versions 5.15.179 to 5.15.224, 6.1.129 to 6.1.191, 6.6.79 to 6.6.160, and 6.12.16 to 6.12.113. An attacker with CAP_NET_ADMIN privileges in the network namespace can exploit this vulnerability.

Summarized by @cf/meta/llama-3.3-70b-instruct-fp8-fast. Verify details against the original sources.

Attack conditions

Replacement requires CAP_NET_ADMIN in the network namespace.

Excerpt from the original source description below.

Review supporting sources →

Affected versions

Check the exact model, release, and any platform requirements against your installation.

Linux · Linux

Linux

11 ranges
Linux version evidence

Compare with this publisher’s ranges. This does not inspect your installation.

affected

fc07a232326a623d0be482e307c08ea7049c2846 → before 82d83eec893d8ae84f280aec44c60d9fdecc62b5

git versions

b1f7bdee5750d6cbb9497140cd6582abc5fdcb9e → before a411df69524f91fe3adb8f9544d33e701fc9732c

git versions

3bed2abab4a682d426624ce9add9d7b6d475d4e4 → before 7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4a

git versions

7f5005457b3072fe1ddf15bfef869f2a1d98e05e → before c60d17d6dd61adc761ac6f65a008fefbc54cbf87

git versions

7d3f3b4367f315a61fc615e3138f3d320da8c466 → before c6d670ac656badfd0e15355e07a13a6bdf3b69fd

git versions

7d3f3b4367f315a61fc615e3138f3d320da8c466 → before f27483f9975b5065ff67054cc7eb8edac6083488

git versions

7d3f3b4367f315a61fc615e3138f3d320da8c466 → before 6619e01855e65ef35723685a557e3eb106f4ecf5

git versions

5.15.179 → before 5.15.224

semver versions

6.1.129 → before 6.1.191

semver versions

6.6.79 → before 6.6.160

semver versions

6.12.16 → before 6.12.113

semver versions

unaffected

unknown

Other versions: unaffected

Linux · Linux

Linux

9 ranges
Linux version evidence

Compare with this publisher’s ranges. This does not inspect your installation.

affected

6.13

unaffected

0 → before 6.13

semver versions

5.15.224 → through 5.15.*

semver versions

6.1.191 → through 6.1.*

semver versions

6.6.160 → through 6.6.*

semver versions

6.12.113 → through 6.12.*

semver versions

6.18.57 → through 6.18.*

semver versions

7.2.11 → through 7.2.*

semver versions

7.3 → through *

original_commit_for_fix versions

unknown

Other versions: affected

Automatic dependency matching is unavailable for this record. Use the product evidence and publisher’s instructions to check your installation.

What to do

Compare your installed product and version with the affected versions above. A matching product name alone does not confirm exposure.

No structured fix or remediation guidance is available here. Check the full source description and vendor’s latest advisory for a patch or workaround; do not assume another version is safe.

cve.new guidance unless attributed to a publisher. This page does not inspect your installation.

Public exploit evidence

No public exploit reference is identified in the imported evidence. This is not a claim that no exploit exists.

Original source description

Read the full publisher description

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

7 sources
git.kernel.org/stable/c/82d83eec893d8ae84f280aec44c60d9fdecc62b5
Source referenceLinux
git.kernel.org/stable/c/a411df69524f91fe3adb8f9544d33e701fc9732c
Source referenceLinux
git.kernel.org/stable/c/7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4a
Source referenceLinux
git.kernel.org/stable/c/c60d17d6dd61adc761ac6f65a008fefbc54cbf87
Source referenceLinux
git.kernel.org/stable/c/c6d670ac656badfd0e15355e07a13a6bdf3b69fd
Source referenceLinux
git.kernel.org/stable/c/f27483f9975b5065ff67054cc7eb8edac6083488
Source referenceLinux
View 1 more references
git.kernel.org/stable/c/6619e01855e65ef35723685a557e3eb106f4ecf5
Source referenceLinux

Inside the record

Evidence available

Package identity · not supplied
Version evidence
Remediation guidance · not supplied
Weakness classification · not supplied
Additional publishers · not supplied

Describes the evidence in this view, not whether the product is safe.

Original records

CVE-2026-99074

View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.

cve.new JSON →

Environment requirements

These conditions apply together as specified by the publisher. A matching product name alone does not establish exposure.

Linux · platform conditions

Any condition may hold

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 5.15.179

Before: 5.15.224

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 6.1.129

Before: 6.1.191

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 6.6.79

Before: 6.6.160

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 6.12.16

Before: 6.12.113

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 6.13

Before: 6.18.57

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 6.13

Before: 7.2.11

Vulnerable product

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

From (inclusive): 6.13

Before: 7.3

Applicability preview
[
  {
    "nodes": [
      {
        "operator": "OR",
        "negate": false,
        "cpeMatch": [
          {
            "vulnerable": true,
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "5.15.179",
            "versionEndExcluding": "5.15.224"
          },
          {
            "vulnerable": true,
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "6.1.129",
            "versionEndExcluding": "6.1.191"
          },
          {
            "vulnerable": true,
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "6.6.79",
            "versionEndExcluding": "6.6.160"
          },
          {
            "vulnerable": true,
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "6.12.16",
            "versionEndExcluding": "6.12.113"
          },
          {
            "vulnerable": true,
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "6.13",
            "versionEndExcluding": "6.18.57"
          },
          {
            "vulnerable": true,
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "6.13",
            "versionEndExcluding": "7.2.11"
          },
          {
            "vulnerable": true,
            "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "6.13",
            "versionEndExcluding": "7.3"
          }
        ]
      }
    ]
  }
]
Contributing organizations · 1
Linux

Assigning organization

2026-10-30

Timeline

All times UTC

  1. Advisory published

    Publication date supplied by the source.

  2. Source updated

    Latest modification date supplied by the source.

  3. Last imported by cve.new

    Latest catalog import, not the date we first saw this advisory.

What changed

Follow changes
No substantive changes have been recorded here yet. History starts when cve.new observes a change after tracking is enabled; earlier edits are not reconstructed.

Large field values are marked as truncated previews. Original source snapshots remain retained.