CVE-2026-31504

Aliases:UBUNTU-CVE-2026-31504DEBIAN-CVE-2026-31504
Advisory lineage Upstream: 0 Downstream: 140
Modified
Published: 22 Apr 2026, 13:54
Last modified:08 Sept 2026, 08:47

Vulnerability Summary

Overall Risk (default)
medium
31/100
CVSS Score
7.8 HIGH
v3.1 (cve.org)
EPSS Score
0.14% LOW
0% probability 0.00%
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

22 Apr 2026, 13:54
Published
Vulnerability first disclosed
08 Sept 2026, 08:47
Last Modified
Vulnerability information updated

Description

In the Linux kernel, the following vulnerability has been resolved: net: fix fanout UAF in packet_release() via NETDEV_UP race `packet_release()` has a race window where `NETDEV_UP` can re-register a socket into a fanout group's `arr[]` array. The re-registration is not cleaned up by `fanout_release()`, leaving a dangling pointer in the fanout array. `packet_release()` does NOT zero `po->num` in its `bind_lock` section. After releasing `bind_lock`, `po->num` is still non-zero and `po->ifindex` still matches the bound device. A concurrent `packet_notifier(NETDEV_UP)` that already found the socket in `sklist` can re-register the hook. For fanout sockets, this re-registration calls `__fanout_link(sk, po)` which adds the socket back into `f->arr[]` and increments `f->num_members`, but does NOT increment `f->sk_ref`. The fix sets `po->num` to zero in `packet_release` while `bind_lock` is held to prevent NETDEV_UP from linking, preventing the race window. This bug was found following an additional audit with Claude Code based on CVE-2025-38617.

CVSS Metrics

  • v4.0•HIGH•Score: 7.3CVSS:4.0/AV:L/AC:H/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
  • v3.1•HIGH•Score: 7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Trends

Current EPSS score: 0.14%• Percentile: 3%

Techniques & Countermeasures

  • CWE-416•Use After Free

    The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

Affected Systems

  • debian•linux

    < 5.10.257-1 | < 6.1.170-1 | < 6.12.85-1 | < 6.19.11-1

  • debian•linux-6.1

    < 6.1.170-1~deb11u1

  • ubuntu•linux

    all | < 4.4.0-281.315 | < 4.15.0-250.262 | < 5.4.0-230.250 | < 5.15.0-179.189 | < 6.8.0-117.117 | < 6.17.0-29.29

  • ubuntu•linux-allwinner-5.19

    all

  • ubuntu•linux-aws

    < 4.4.0-1155.161 | < 4.4.0-1193.208 | < 4.15.0-1192.205 | < 5.4.0-1159.169 | < 5.15.0-1108.115 | < 6.8.0-1055.58 | < 6.17.0-1015.15

  • ubuntu•linux-aws-5.0

    all

  • ubuntu•linux-aws-5.11

    all

  • ubuntu•linux-aws-5.13

    all

  • ubuntu•linux-aws-5.15

    < 5.15.0-1108.115~20.04.1

  • ubuntu•linux-aws-5.19

    all

  • ubuntu•linux-aws-5.3

    all

  • ubuntu•linux-aws-5.4

    < 5.4.0-1160.170~18.04.1

  • ubuntu•linux-aws-5.8

    all

  • ubuntu•linux-aws-6.14

    all

  • ubuntu•linux-aws-6.17

    < 6.17.0-1017.17~24.04.1

  • ubuntu•linux-aws-6.2

    all

  • ubuntu•linux-aws-6.5

    all

  • ubuntu•linux-aws-6.8

    < 6.8.0-1057.60~22.04.1

  • ubuntu•linux-aws-fips

    < 4.15.0-2130.136 | all | < 5.4.0-1159.169+fips1 | < 5.15.0-1108.115+fips1 | < 6.8.0-1055.58+fips1

  • ubuntu•linux-aws-hwe

    < 4.15.0-1192.205~16.04.1

  • ubuntu•linux-azure

    < 4.15.0-1201.216~14.04.1 | all | < 5.4.0-1163.169 | < 5.15.0-1114.123 | < 6.8.0-1056.62 | < 6.17.0-1015.15

  • ubuntu•linux-azure-4.15

    < 4.15.0-1201.216

  • ubuntu•linux-azure-5.11

    all

  • ubuntu•linux-azure-5.13

    all

  • ubuntu•linux-azure-5.15

    < 5.15.0-1114.123~20.04.1

  • ubuntu•linux-azure-5.19

    all

  • ubuntu•linux-azure-5.3

    all

  • ubuntu•linux-azure-5.4

    < 5.4.0-1163.169~18.04.1

  • ubuntu•linux-azure-5.8

    all

  • ubuntu•linux-azure-6.11

    all

  • ubuntu•linux-azure-6.14

    all

  • ubuntu•linux-azure-6.17

    < 6.17.0-1015.15~24.04.1

  • ubuntu•linux-azure-6.2

    all

  • ubuntu•linux-azure-6.5

    all

  • ubuntu•linux-azure-6.8

    < 6.8.0-1059.65~22.04.1

  • ubuntu•linux-azure-edge

    all

  • ubuntu•linux-azure-fde

    all | all | all | all

  • ubuntu•linux-azure-fde-5.19

    all

  • ubuntu•linux-azure-fde-6.14

    all

  • ubuntu•linux-azure-fde-6.2

    all

  • ubuntu•linux-azure-fde-6.8

    all

  • ubuntu•linux-azure-fips

    < 4.15.0-2110.116 | all | < 5.4.0-1163.169+fips1 | < 5.15.0-1114.123+fips1 | < 6.8.0-1059.65+fips1

  • ubuntu•linux-azure-nvidia

    all

  • ubuntu•linux-azure-nvidia-6.14

    all

  • ubuntu•linux-bluefield

    all | < 5.4.0-1118.125 | < 5.15.0-1092.94 | < 6.8.0-1022.26

  • ubuntu•linux-fips

    < 4.4.0-1125.132 | all | < 4.15.0-1147.159 | < 5.4.0-1133.143 | < 5.15.0-179.189+fips1 | < 6.8.0-124.124+fips1

  • ubuntu•linux-gcp

    < 4.15.0-1185.202~16.04.1 | all | < 5.4.0-1162.171 | < 5.15.0-1108.117 | < 6.8.0-1058.61 | < 6.17.0-1018.19

  • ubuntu•linux-gcp-4.15

    < 4.15.0-1185.202

  • ubuntu•linux-gcp-5.11

    all

  • ubuntu•linux-gcp-5.13

    all

Showing first 50 affected entries in server-rendered view.

References (48)