# CVE-2026-31400: sunrpc: fix cache_request leak in cache_release

> A memory leak in the Linux kernel's sunrpc module allows attackers to exhaust system memory by closing file descriptors during cache reads, causing denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 3 Apr 2026
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2026-31400, DEBIAN-CVE-2026-31400, GHSA-73jc-99jj-ch5v, ROOT-OS-DEBIAN-11-CVE-2026-31400, ROOT-OS-DEBIAN-12-CVE-2026-31400, ROOT-OS-DEBIAN-13-CVE-2026-31400, ROOT-OS-UBUNTU-2204-CVE-2026-31400, ROOT-OS-UBUNTU-2404-CVE-2026-31400, UBUNTU-CVE-2026-31400

## What is CVE-2026-31400?

CVE-2026-31400 is a medium-severity denial of service vulnerability in Linux kernel, published on 3 Apr 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:

sunrpc: fix cache_request leak in cache_release

When a reader's file descriptor is closed while in the middle of reading
a cache_request (rp->offset != 0), cache_release() decrements the
request's readers count but never checks whether it should free the
request.

In cache_read(), when readers drops to 0 and CACHE_PENDING is clear, the
cache_request is removed from the queue and freed along with its buffer
and cache_head reference. cache_release() lacks this cleanup.

The only other path that frees requests with readers == 0 is
cache_dequeue(), but it runs only when CACHE_PENDING transitions from
set to clear. If that transition already happened while readers was
still non-zero, cache_dequeue() will have skipped the request, and no
subsequent call will clean it up.

Add the same cleanup logic from cache_read() to cache_release(): after
decrementing readers, check if it reached 0 with CACHE_PENDING clear,
and if so, dequeue and free the cache_request.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2026-31400?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31400?

Apply the vendor's patch.

## Is CVE-2026-31400 being exploited?

There is no known exploitation of CVE-2026-31400 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31400 and fix it if it is affected.

What it is: CVE-2026-31400 is a medium-severity denial of service vulnerability in Linux kernel, published on 3 Apr 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-2026-31400 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-31400/ (Markdown: https://insights.sbomify.com/CVE-2026-31400/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31400
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31400
- OSV: https://osv.dev/vulnerability/CVE-2026-31400

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31400/
Summaries are generated and may contain mistakes; the official description above is the record.