# CVE-2026-87734: Denial of service in utcp

> Remote attackers can cause denial of service in applications using the utcp OCaml library via out-of-order segment reassembly.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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:** Not needed
- **Fix available:** Yes
- **Published:** 9 Sep 2026
- **Updated:** 14 Sep 2026
- **Also known as:** GHSA-798p-53r8-rvx4, OSEC-2026-11

## What is CVE-2026-87734?

CVE-2026-87734 is a high-severity denial of service vulnerability in OCaml utcp, published on 9 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in the utcp package before 0.0.6 for OCaml. Out-of-order segment reassembly allows remote denial of service.

Weakness: CWE-923 (Improper Restriction of Communication Channel to Intended Endpoints)

## Which versions are affected by CVE-2026-87734?


## How do I fix CVE-2026-87734?

Upgrade to a fixed version.

## Is CVE-2026-87734 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-87734 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-87734 and fix it if it is affected.

What it is: CVE-2026-87734 is a high-severity denial of service vulnerability in OCaml utcp, published on 9 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-87734 exists.

Affected product: OCaml utcp. 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-2026-87734/ (Markdown: https://insights.sbomify.com/CVE-2026-87734/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-87734
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-87734
- OSV: https://osv.dev/vulnerability/CVE-2026-87734

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-87734/
Summaries are generated and may contain mistakes; the official description above is the record.