CVE-2025-40214

Aliases:UBUNTU-CVE-2025-40214DEBIAN-CVE-2025-40214
Advisory lineage Upstream: 0 Downstream: 23
Deferred
Published: 04 Dec 2025, 12:38
Last modified:05 Aug 2026, 12:08

Vulnerability Summary

Overall Risk (default)
medium
31/100
CVSS Score
7.8 HIGH
v3.1 (cve.org)
EPSS Score
0.15% LOW
0% probability +0.11%
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

04 Dec 2025, 12:38
Published
Vulnerability first disclosed
05 Aug 2026, 12:08
Last Modified
Vulnerability information updated

Description

In the Linux kernel, the following vulnerability has been resolved: af_unix: Initialise scc_index in unix_add_edge(). Quang Le reported that the AF_UNIX GC could garbage-collect a receive queue of an alive in-flight socket, with a nice repro. The repro consists of three stages. 1) 1-a. Create a single cyclic reference with many sockets 1-b. close() all sockets 1-c. Trigger GC 2) 2-a. Pass sk-A to an embryo sk-B 2-b. Pass sk-X to sk-X 2-c. Trigger GC 3) 3-a. accept() the embryo sk-B 3-b. Pass sk-B to sk-C 3-c. close() the in-flight sk-A 3-d. Trigger GC As of 2-c, sk-A and sk-X are linked to unix_unvisited_vertices, and unix_walk_scc() groups them into two different SCCs: unix_sk(sk-A)->vertex->scc_index = 2 (UNIX_VERTEX_INDEX_START) unix_sk(sk-X)->vertex->scc_index = 3 Once GC completes, unix_graph_grouped is set to true. Also, unix_graph_maybe_cyclic is set to true due to sk-X's cyclic self-reference, which makes close() trigger GC. At 3-b, unix_add_edge() allocates unix_sk(sk-B)->vertex and links it to unix_unvisited_vertices. unix_update_graph() is called at 3-a. and 3-b., but neither unix_graph_grouped nor unix_graph_maybe_cyclic is changed because both sk-B's listener and sk-C are not in-flight. 3-c decrements sk-A's file refcnt to 1. Since unix_graph_grouped is true at 3-d, unix_walk_scc_fast() is finally called and iterates 3 sockets sk-A, sk-B, and sk-X: sk-A -> sk-B (-> sk-C) sk-X -> sk-X This is totally fine. All of them are not yet close()d and should be grouped into different SCCs. However, unix_vertex_dead() misjudges that sk-A and sk-B are in the same SCC and sk-A is dead. unix_sk(sk-A)->scc_index == unix_sk(sk-B)->scc_index <-- Wrong! && sk-A's file refcnt == unix_sk(sk-A)->vertex->out_degree ^-- 1 in-flight count for sk-B -> sk-A is dead !? The problem is that unix_add_edge() does not initialise scc_index. Stage 1) is used for heap spraying, making a newly allocated vertex have vertex->scc_index == 2 (UNIX_VERTEX_INDEX_START) set by unix_walk_scc() at 1-c. Let's track the max SCC index from the previous unix_walk_scc() call and assign the max + 1 to a new vertex's scc_index. This way, we can continue to avoid Tarjan's algorithm while preventing misjudgments.

CVSS Metrics

  • 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: 0.15%• Percentile: 4%

Affected Systems

  • debian•linux

    < 6.1.159-1 | < 6.12.63-1 | < 6.17.9-1

  • debian•linux-6.1

    < 6.1.159-1~deb11u1

  • ubuntu•linux

    < 6.17.0-12.12

  • ubuntu•linux-allwinner-5.19

    all

  • ubuntu•linux-aws

    < 6.17.0-1006.6

  • ubuntu•linux-aws-5.0

    all

  • ubuntu•linux-aws-5.11

    all

  • ubuntu•linux-aws-5.13

    all

  • ubuntu•linux-aws-5.19

    all

  • ubuntu•linux-aws-5.3

    all

  • ubuntu•linux-aws-5.8

    all

  • ubuntu•linux-aws-6.14

    all

  • ubuntu•linux-aws-6.17

    < 6.17.0-1007.7~24.04.1

  • ubuntu•linux-aws-6.2

    all

  • ubuntu•linux-aws-6.5

    all

  • ubuntu•linux-azure

    all | < 6.17.0-1007.7

  • ubuntu•linux-azure-5.11

    all

  • ubuntu•linux-azure-5.13

    all

  • ubuntu•linux-azure-5.19

    all

  • ubuntu•linux-azure-5.3

    all

  • ubuntu•linux-azure-5.8

    all

  • ubuntu•linux-azure-6.11

    all

  • ubuntu•linux-azure-6.14

    all

  • ubuntu•linux-azure-6.2

    all

  • ubuntu•linux-azure-6.5

    all

  • ubuntu•linux-azure-edge

    all

  • ubuntu•linux-azure-fde

    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-nvidia-6.14

    all

  • ubuntu•linux-bluefield

    all

  • ubuntu•linux-gcp

    all | < 6.17.0-1006.6

  • ubuntu•linux-gcp-5.11

    all

  • ubuntu•linux-gcp-5.13

    all

  • ubuntu•linux-gcp-5.19

    all

  • ubuntu•linux-gcp-5.3

    all

  • ubuntu•linux-gcp-5.8

    all

  • ubuntu•linux-gcp-6.11

    all

  • ubuntu•linux-gcp-6.14

    all

  • ubuntu•linux-gcp-6.17

    < 6.17.0-1008.8~24.04.1

  • ubuntu•linux-gcp-6.2

    all

  • ubuntu•linux-gcp-6.5

    all

  • ubuntu•linux-gke

    all

  • ubuntu•linux-gke-4.15

    all

  • ubuntu•linux-gke-5.15

    all

  • ubuntu•linux-gke-5.4

    all

  • ubuntu•linux-gkeop

    all

  • ubuntu•linux-gkeop-5.15

    all

  • ubuntu•linux-gkeop-5.4

    all

Showing first 50 affected entries in server-rendered view.

References (12)