# CVE-2026-90157: bpf: Reject negative optlen in cgroup getsockopt hook

> A local attacker with low privileges can trigger a kernel warning and potential denial of service by providing a negative option length in a cgroup getsockopt BPF hook.

- **Severity:** Not scored
- **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:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-102590, BELL-CVE-2026-90157, DEBIAN-CVE-2026-90157, GHSA-v6r2-3cg3-jrp9, UBUNTU-CVE-2026-90157

## What is CVE-2026-90157?

CVE-2026-90157 is a vulnerability in Linux, published on 17 Sep 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:

bpf: Reject negative optlen in cgroup getsockopt hook

A cgroup getsockopt BPF program can shrink ctx->optlen after the
kernel getsockopt handler has run. The kernel-buffer variant, used by
TCP_ZEROCOPY_RECEIVE, only rejects values larger than the original
length.

If BPF writes a negative optlen, that value is accepted and propagated
back to the TCP getsockopt code. It can then be passed to
copy_to_sockptr() as a size_t and trigger the hardened usercopy
bytes > INT_MAX warning.

Reject negative ctx.optlen in __cgroup_bpf_run_filter_getsockopt_kern(),
matching the lower-bound validation already present in the sockptr-based
getsockopt hook.

## Which versions are affected by CVE-2026-90157?


## How do I fix CVE-2026-90157?

Apply the vendor's patch.

## Is CVE-2026-90157 being exploited?

There is no known exploitation of CVE-2026-90157 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90157 and fix it if it is affected.

What it is: CVE-2026-90157 is a vulnerability in Linux, published on 17 Sep 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-2026-90157 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-2026-90157/ (Markdown: https://insights.sbomify.com/CVE-2026-90157/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90157
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90157
- OSV: https://osv.dev/vulnerability/CVE-2026-90157

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90157/
Summaries are generated and may contain mistakes; the official description above is the record.