CVE-2025-37756: net: tls: explicitly disallow disconnect

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-05-01 · updated 2026-10-15

Description

In the Linux kernel, the following vulnerability has been resolved: net: tls: explicitly disallow disconnect syzbot discovered that it can disconnect a TLS socket and then run into all sort of unexpected corner cases. I have a vague recollection of Eric pointing this out to us a long time ago. Supporting disconnect is really hard, for one thing if offload is enabled we'd need to wait for all packets to be _acked_. Disconnect is not commonly used, disallow it. The immediate problem syzbot run into is the warning in the strp, but that's just the easiest bug to trigger: WARNING: CPU: 0 PID: 5834 at net/tls/tls_strp.c:486 tls_strp_msg_load+0x72e/0xa80 net/tls/tls_strp.c:486 RIP: 0010:tls_strp_msg_load+0x72e/0xa80 net/tls/tls_strp.c:486 Call Trace: <TASK> tls_rx_rec_wait+0x280/0xa60 net/tls/tls_sw.c:1363 tls_sw_recvmsg+0x85c/0x1c30 net/tls/tls_sw.c:2043 inet6_recvmsg+0x2c9/0x730 net/ipv6/af_inet6.c:678 sock_recvmsg_nosec net/socket.c:1023 [inline] sock_recvmsg+0x109/0x280 net/socket.c:1045 __sys_recvfrom+0x202/0x380 net/socket.c:2237

Affected products

Debian Linux: 11.0
Linux kernel: from 4.13 before 5.10.237; from 5.11 before 5.15.181; from 5.16 before 6.1.135; from 6.2 before 6.6.88; from 6.7 before 6.12.24; from 6.13 before 6.13.12 — fixed in 5.10.237, 5.15.181, 6.1.135, 6.12.24, 6.13.12, 6.14.3

How to fix

Upgrade to a fixed version: Linux kernel 5.10.237, 5.15.181, 6.1.135, 6.12.24. Check the vendor advisory for mitigations.

References

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