Bug 2516865 (CVE-2026-74378)

Summary: CVE-2026-74378 kernel: RDMA/rxe: Fix TOCTOU heap overflow in get_srq_wqe
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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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's RDMA/rxe component. A Time-of-check to time-of-use (TOCTOU) vulnerability exists where a user-space thread can modify the `num_sge` value after it has been validated but before it is used to calculate a memory copy size. This allows a local attacker to trigger a heap buffer overflow when copying a Work Queue Entry (WQE), potentially leading to a denial of service or arbitrary code execution.
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Description OSIDB Bzimport 2026-08-15 06:37:31 UTC 
In the Linux kernel, the following vulnerability has been resolved:

RDMA/rxe: Fix TOCTOU heap overflow in get_srq_wqe

get_srq_wqe() reads wqe->dma.num_sge from the shared receive queue
buffer, which is mapped into userspace. It validates num_sge against
max_sge, but then re-reads the same field to calculate the memcpy
size. A concurrent userspace thread can modify num_sge between
validation and use, causing a heap buffer overflow when copying the
WQE into qp->resp.srq_wqe.

Read num_sge into a local variable and use it for both the bounds
check and the size calculation.
Comment 1 Keith Grant 2026-08-20 19:41:16 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081504-CVE-2026-74378-ceaf@gregkh/T