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CVE-2026-31411

net: atm: fix crash due to unvalidated vcc pointer in sigd_send()

MEDIUM 5.5

At a glance

Source
NVD
EPSS
EPSS 0.13 % · percentile 3 ()
State
PUBLISHED
Published
Updated
Assigner
Linux
NVD status
Modified

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

Weaknesses (CWE)

  • CWE-476 — NULL Pointer Dereference

References

Scores

VersionScoreVectorScored by
CVSS 3.1MEDIUM 5.5CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:HNVD · nvd@nist.gov (Primary)

European references

CERT-FR advisories

Affected configurations (NVD CPE)

Affected products

ProductVersions
Linux · Linuxaffected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < c96549d07dfdd51aadf0722cfb40711574424840 ; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 1c8bda3df028d5e54134077dcd09f46ca8cfceb5 ; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 3e1a8b00095246a9a2b46b57f6d471c6d3c00ed2 ; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < e3f80666c2739296c3b69a127300455c43aa1067 ; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 21c303fec138c002f90ed33bce60e807d53072bb ; affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 69d3f9ee5489e6e8b66defcfa226e91d82393297
Linux · Linuxaffected 2.6.12 ; unaffected 0 < 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.*

Sources

SourceLicence
CVE List (CVEProject cvelistV5)CVE Program Terms of Use
EPSS (FIRST.org)FIRST — attribution requested
ENISA EUVDENISA — reproduction authorised, source acknowledged
CERT-FR (ANSSI)Licence Ouverte / Etalab 2.0
NVD (NIST) via fkie-cad/nvd-json-data-feedsPublic domain — this product uses data from the NVD API but is not endorsed or certified by the NVD