CVE-2025-38544: rxrpc: Fix bug due to prealloc collision

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-08-16 · updated 2026-10-30
Weakness: CWE-617

Description

In the Linux kernel, the following vulnerability has been resolved: rxrpc: Fix bug due to prealloc collision When userspace is using AF_RXRPC to provide a server, it has to preallocate incoming calls and assign to them call IDs that will be used to thread related recvmsg() and sendmsg() together. The preallocated call IDs will automatically be attached to calls as they come in until the pool is empty. To the kernel, the call IDs are just arbitrary numbers, but userspace can use the call ID to hold a pointer to prepared structs. In any case, the user isn't permitted to create two calls with the same call ID (call IDs become available again when the call ends) and EBADSLT should result from sendmsg() if an attempt is made to preallocate a call with an in-use call ID. However, the cleanup in the error handling will trigger both assertions in rxrpc_cleanup_call() because the call isn't marked complete and isn't marked as having been released. Fix this by setting the call state in rxrpc_service_prealloc_one() and then marking it as being released before calling the cleanup function.

Affected products

Linux kernel: from 4.9 before 6.6.99; from 6.7 before 6.12.39; from 6.13 before 6.15.7; 6.16-rc1, 6.16-rc2, 6.16-rc3, 6.16-rc4, 6.16-rc5 — fixed in 6.6.99, 6.12.39, 6.15.7
Linux: 4.9 — fixed in 6.16

How to fix

Upgrade to a fixed version: Linux kernel 6.6.99, 6.12.39, 6.15.7; Linux 6.16. Check the vendor advisory for mitigations.

References

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