Bug 2516929 (CVE-2026-74436)

Summary: CVE-2026-74436 kernel: rxrpc: serialize kernel accept preallocation with socket teardown
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel. A synchronization issue in the rxrpc component, specifically between `rxrpc_kernel_charge_accept()` and `rxrpc_discard_prealloc()`, can lead to a use-after-free vulnerability. A local attacker could potentially exploit this flaw, causing a kernel preallocation worker to access freed memory. This could result in system instability or a denial of service (DoS).
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Description OSIDB Bzimport 2026-08-15 06:40:54 UTC 
In the Linux kernel, the following vulnerability has been resolved:

rxrpc: serialize kernel accept preallocation with socket teardown

rxrpc_kernel_charge_accept() reads rx->backlog without any
socket/backlog synchronization and passes that raw pointer into
rxrpc_service_prealloc_one(). A concurrent rxrpc_discard_prealloc()
sets rx->backlog = NULL and frees the backlog rings, so a kernel
preallocation worker can keep using a freed struct rxrpc_backlog
while updating *_backlog_head/tail and array slots.

Serialize the state check and backlog lookup with the socket lock,
and reject kernel preallocation once teardown has disabled
listening or discarded the service backlog.
Comment 1 Keith Grant 2026-08-20 23:16:17 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081515-CVE-2026-74436-228e@gregkh/T