# CVE-2026-88359: Denial of service in n/a

> A stack exhaustion vulnerability in libfyaml allows attackers to cause a denial of service via crafted YAML documents.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/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:** No
- **Published:** 24 Sep 2026
- **Updated:** 25 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-88359, GHSA-3qj9-89fg-m5cw, UBUNTU-CVE-2026-88359

## What is CVE-2026-88359?

CVE-2026-88359 is a medium-severity denial of service vulnerability in n/a, published on 24 Sep 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

libfyaml 0.9.6 contains a stack exhaustion vulnerability in fy_atom_iter_format(). When processing a specially crafted YAML document containing a very large literal or folded block scalar, the function repeatedly grows an internal buffer using alloca() inside a loop. The allocated stack memory is not released until the function returns, causing cumulative stack growth that can exceed the process stack limit and result in SIGSEGV and denial of service.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-88359?


## How do I fix CVE-2026-88359?

No fix has been published for CVE-2026-88359 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-88359 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-88359 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-88359 and fix it if it is affected.

What it is: CVE-2026-88359 is a medium-severity denial of service vulnerability in n/a, published on 24 Sep 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: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-88359 exists.

Affected product: n/a. 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-2026-88359/ (Markdown: https://insights.sbomify.com/CVE-2026-88359/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-88359
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-88359
- OSV: https://osv.dev/vulnerability/CVE-2026-88359

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-88359/
Summaries are generated and may contain mistakes; the official description above is the record.