CVE-2026-31411net: atm: fix crash due to unvalidated vcc pointer in sigd_send()

Description

In the Linux kernel, the following vulnerability has been resolved: net: atm: fix crash due to unvalidated vcc pointer in sigd_send() Reproducer available at [1]. The ATM send path (sendmsg -> vcc_sendmsg -> sigd_send) reads the vcc pointer from msg->vcc and uses it directly without any validation. This pointer comes from userspace via sendmsg() and can be arbitrarily forged: int fd = socket(AF_ATMSVC, SOCK_DGRAM, 0); ioctl(fd, ATMSIGD_CTRL); // become ATM signaling daemon struct msghdr msg = { .msg_iov = &iov, ... }; *(unsigned long *)(buf + 4) = 0xdeadbeef; // fake vcc pointer sendmsg(fd, &msg, 0); // kernel dereferences 0xdeadbeef In normal operation, the kernel sends the vcc pointer to the signaling daemon via sigd_enq() when processing operations like connect(), bind(), or listen(). The daemon is expected to return the same pointer when responding. However, a malicious daemon can send arbitrary pointer values. Fix this by introducing find_get_vcc() which validates the pointer by searching through vcc_hash (similar to how sigd_close() iterates over all VCCs), and acquires a reference via sock_hold() if found. Since struct atm_vcc embeds struct sock as its first member, they share the same lifetime. Therefore using sock_hold/sock_put is sufficient to keep the vcc alive while it is being used. Note that there may be a race with sigd_close() which could mark the vcc with various flags (e.g., ATM_VF_RELEASED) after find_get_vcc() returns. However, sock_hold() guarantees the memory remains valid, so this race only affects the logical state, not memory safety. [1]: https://gist.github.com/mrpre/1ba5949c45529c511152e2f4c755b0f3

Timeline

Scores

EPSS (exploitation in 30 days)

0.13% · top 97% of all CVEs (14 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.5.

Affected products

• Linux · Linux

  • affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < c96549d07dfdd51aadf0722cfb40711574424840
  • affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < 1c8bda3df028d5e54134077dcd09f46ca8cfceb5
  • affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < 3e1a8b00095246a9a2b46b57f6d471c6d3c00ed2
  • affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < e3f80666c2739296c3b69a127300455c43aa1067
  • affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < 21c303fec138c002f90ed33bce60e807d53072bb
  • affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < 69d3f9ee5489e6e8b66defcfa226e91d82393297
  • affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < 440c9a5fc477a8ee259d8bf669531250b8398651
  • affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 – < ae88a5d2f29b69819dc7b04086734439d074a643

• Linux · Linux

  • affected 2.6.12
  • unaffected < 2.6.12
  • unaffected 5.10.252 – ≤ 5.10.*
  • unaffected 5.15.202 – ≤ 5.15.*
  • unaffected 6.1.165 – ≤ 6.1.*
  • unaffected 6.6.128 – ≤ 6.6.*
  • unaffected 6.12.75 – ≤ 6.12.*
  • unaffected 6.18.14 – ≤ 6.18.*
  • unaffected 6.19.4 – ≤ 6.19.*
  • unaffected 7.0 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-20469 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-31411](https://cveledger.app/badge/CVE-2026-31411.svg)](https://cveledger.app/cve/CVE-2026-31411)

Record last updated 10 Nov 2026, 12:43 UTC.