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

> A logic error in the Linux kernel's mlx5e driver causes an integer underflow in eswitch mode blocks during IPsec SA acquisition, potentially leading to denial of service.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 25 Jul 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-64522, DEBIAN-CVE-2026-64522, GHSA-x5f7-rh4c-gxvr, ROOT-OS-UBUNTU-2204-CVE-2026-64522, UBUNTU-CVE-2026-64522

## What is CVE-2026-64522?

CVE-2026-64522 is a high-severity vulnerability in Linux, published on 25 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2026-64522?


## How do I fix CVE-2026-64522?

Apply the vendor's patch.

## Is CVE-2026-64522 being exploited?

There is no known exploitation of CVE-2026-64522 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64522 and fix it if it is affected.

What it is: CVE-2026-64522 is a high-severity vulnerability in Linux, published on 25 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-64522 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-64522/ (Markdown: https://insights.sbomify.com/CVE-2026-64522/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64522
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64522
- OSV: https://osv.dev/vulnerability/CVE-2026-64522

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64522/
Summaries are generated and may contain mistakes; the official description above is the record.