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

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于sigd_send函数中未验证vcc指针，可能导致内核崩溃。

AI Predicted 7.8 Difficulty: Easy EPSS 0.13% · P2

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< c96549d07dfdd51aadf0722cfb40711574424840 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 1c8bda3df028d5e54134077dcd09f46ca8cfceb5 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 3e1a8b00095246a9a2b46b57f6d471c6d3c00ed2 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< e3f80666c2739296c3b69a127300455c43aa1067 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 21c303fec138c002f90ed33bce60e807d53072bb affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 69d3f9ee5489e6e8b66defcfa226e91d82393297 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< 440c9a5fc477a8ee259d8bf669531250b8398651 affected
1da177e4c3f41524e886b7f1b8a0c1fc7321cac2< ae88a5d2f29b69819dc7b04086734439d074a643 affected
… +10 more rows
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I. Basic Information for CVE-2026-31411

Vulnerability Information
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Vulnerability Title
net: atm: fix crash due to unvalidated vcc pointer in sigd_send()
Source: CVE Program / CVE List V5
Vulnerability 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
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于sigd_send函数中未验证vcc指针，可能导致内核崩溃。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 ~ c96549d07dfdd51aadf0722cfb40711574424840 -
Linux Linux 2.6.12 -

II. Public POCs for CVE-2026-31411

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III. Intelligence Information for CVE-2026-31411

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IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-31411

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