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TI-2026-79867 Aliases CVE-2026-99074GHSA-j9w6-p85x-r6r9

Null pointer dereference in Linux kernel IPv4 PMTU update path

Priority LOW 22Published · Updated

Key facts

Attack vector
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Privileges required
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User interaction
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Attack complexity
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Impact type
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Confidentiality · integrity · availability
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Fix status
Partial Red Hat: 1 without a fix

No CVSS vector from any source. Fix status from CNA and Red Hat.

Summary

The Linux kernel IPv4 path MTU update code for multipath nexthop groups is affected in the commit ranges listed, and from 6.13 onward. When a nexthop group shrinks during the update, the code accepts a path index that no longer exists and dereferences a NULL pointer. Triggering it requires CAP_NET_ADMIN in a network namespace, which a local user can obtain in a new user and network namespace where unprivileged user namespaces are permitted.

Written with Claude Haiku 5.5 from the sources below · 2026-10-30

Description from the CNA

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.

Why it matters now

EPSS 0.00154 4th percentileScored 2026-11-07
Fix Partial Linux (Linux): 5.15.224, 6.1.191, 6.6.160 +4Red Hat: 1 without a fix

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
LinuxLinux5.15.179 to before 5.15.224; 6.1.129 to before 6.1.191; 6.6.79 to before 6.6.160; 6.12.16 to before 6.12.1135.15.224, 6.1.191, 6.6.160, 6.12.113Patch availableCNA
LinuxLinux6.13 and later5.15.224, 6.1.191, 6.6.160, 6.12.113, 6.18.57, 7.2.11, 7.3Patch availableCNA
  • Linux VendorLinux Affected 5.15.179 to before 5.15.224; 6.1.129 to before 6.1.191; 6.6.79 to before 6.6.160; 6.12.16 to before 6.12.113 Fixed in 5.15.224, 6.1.191, 6.6.160, 6.12.113 Patch available CNA
  • Linux VendorLinux Affected 6.13 and later Fixed in 5.15.224, 6.1.191, 6.6.160, 6.12.113, 6.18.57, 7.2.11, 7.3 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*——Linux
  • cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions — — ·Linux

Remediation

Fixed Linux kernel versions are 5.15.224, 6.1.191, 6.6.160, 6.12.113, 6.18.57, 7.2.11 and 7.3. Red Hat Enterprise Linux 6 is affected with no fix planned.

Written with Claude Haiku 5.5 from the sources below · 2026-10-30

  • Fix · CNA Linux (Linux) Fixed in 5.15.224, 6.1.191, 6.6.160, 6.12.113
  • Fix · CNA Linux (Linux) Fixed in 5.15.224, 6.1.191, 6.6.160, 6.12.113, 6.18.57, 7.2.11, 7.3

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 6AffectedNo fix planned: Out of support scope
Not affected: 5 products
  • Red Hat Enterprise Linux 10
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 9
  • Red Hat OpenShift Container Platform 4

Timeline

  1. 2026-10-23 Threatist record created from CVE-2026-99074
  2. 2026-10-23 Alias added: GHSA-j9w6-p85x-r6r9
  3. 2026-10-26 Affected versions changed · Red Hat
  4. 2026-10-26 CVSS score added · Red Hat
  5. 2026-10-30 Fix available: Linux/[email protected], Linux/[email protected], Linux/Linux@82d83eec893d8ae84f280aec44c60d9fdecc62b5 +1 · CNA
  6. 2026-10-30 2 new references · CNA

References

Other 7

  • TI-2025-26358 tls: fix handling of zero-length records on the rx_list KEVCVSS 3.1CRITICAL 9.8
  • TI-2026-38352 netfilter: bridge: make ebt_snat ARP rewrite writable KEVCVSS 3.1HIGH 8.8
  • TI-2021-02452 Incorrect authorization in Ubuntu linux kernel KEVCVSS 3.1HIGH 8.8
  • TI-2013-05264 The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the… KEVCVSS 3.1HIGH 8.8
  • TI-2022-00125 Integer overflow in kernel KEVCVSS 3.1HIGH 8.4
  • TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
See all 21741 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences