# CVE-2026-74590: fsverity: Fix bpf_get_fsverity_digest() dynptr assumptions

> A race condition in the Linux kernel's fsverity BPF helper can cause a crash if digest size is concurrently modified, leading to denial of service.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-74590, DEBIAN-CVE-2026-74590, GHSA-pxx7-9r2r-m5m2, UBUNTU-CVE-2026-74590

## What is CVE-2026-74590?

CVE-2026-74590 is a high-severity vulnerability in Linux, published on 22 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

fsverity: Fix bpf_get_fsverity_digest() dynptr assumptions

The BPF verifier and the dynptr abstraction ensure that the memory space
referenced by a dynptr remains valid.  They do not, however, provide any
guarantee that the contents of the memory are stable.  kfuncs are
expected to remain memory-safe even if concurrent modifications occur.

bpf_get_fsverity_digest() didn't follow that: it could crash if
arg->digest_size was concurrently modified.

Fix that by using the known-good value hash_alg->digest_size instead.

Also widen 'dynptr_sz' and 'out_digest_sz' to u64 to match the return
type of __bpf_dynptr_size().  It doesn't appear that it can actually be
more than INT_MAX currently (since __bpf_dynptr_data_rw() excludes
file-based pointers), but the correct type might as well be used.

## Which versions are affected by CVE-2026-74590?


## How do I fix CVE-2026-74590?

Apply the vendor's patch.

## Is CVE-2026-74590 being exploited?

There is no known exploitation of CVE-2026-74590 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74590 and fix it if it is affected.

What it is: CVE-2026-74590 is a high-severity vulnerability in Linux, published on 22 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-74590 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-2026-74590/ (Markdown: https://insights.sbomify.com/CVE-2026-74590/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74590
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74590
- OSV: https://osv.dev/vulnerability/CVE-2026-74590

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74590/
Summaries are generated and may contain mistakes; the official description above is the record.