# CVE-2026-87732: Other in mirage-crypto

> Attackers can read decrypted plaintext from a buffer even when authentication tags are forged, bypassing integrity checks in the mirage-crypto library.

- **Severity:** Medium 6.2 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 9 Sep 2026
- **Updated:** 9 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-87732, GHSA-vqxm-cgmv-2pcr, OSEC-2026-12, UBUNTU-CVE-2026-87732

## What is CVE-2026-87732?

CVE-2026-87732 is a medium-severity vulnerability in OCaml mirage-crypto, published on 9 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An issue was discovered in the mirage-crypto package before 2.2.0 for OCaml. The AES.GCM.authenticate_decrypt_into and Chacha20.authenticate_decrypt_into functions write the decrypted plaintext into a caller-provided buffer and only then compares the tag. On a forged tag, the functions returns false, but the destination buffer already holds the full plaintext.

Weakness: CWE-347 (Improper Verification of Cryptographic Signature)

## Which versions are affected by CVE-2026-87732?


## How do I fix CVE-2026-87732?

Upgrade to a fixed version.

## Is CVE-2026-87732 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-87732 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-87732 and fix it if it is affected.

What it is: CVE-2026-87732 is a medium-severity vulnerability in OCaml mirage-crypto, published on 9 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-87732 exists.

Affected product: OCaml mirage-crypto. 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-2026-87732/ (Markdown: https://insights.sbomify.com/CVE-2026-87732/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-87732
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-87732
- OSV: https://osv.dev/vulnerability/CVE-2026-87732

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-87732/
Summaries are generated and may contain mistakes; the official description above is the record.