# CVE-2026-87736: Mirage-Crypto-EC out-of-bounds read in EC public key parsing

Source: https://junglewise.ai/threats/cve-2026-87736-mirage-crypto-ec-out-of-bounds-read-in-ec-public-key-parsing  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-09. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-87736 · Severity: medium · CVSS 4.3 · Published 2026-09-09

Mirage-Crypto-EC is a cryptographic library for OCaml that handles elliptic curve operations, including digital signature verification and key exchange. A missing length check in the library allows an attacker to trigger an out-of-bounds memory read by providing a malformed compressed EC public key, potentially causing the application to crash or leak sensitive data from memory.

Technologies: [OCaml Mirage-Crypto-Ec](https://junglewise.ai/threats/technologies/mirage-crypto-ec). Vendors: [OCaml](https://junglewise.ai/threats/vendors/ocaml).

## Quick answers

**Is CVE-2026-87736 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-87736 being exploited in the wild.

**How severe is CVE-2026-87736?** Medium severity, with a CVSS score of 4.3, published 9 September 2026.

**Which products and versions are affected?** OCaml Mirage-Crypto-Ec before 2.3.0.

**Is there a fix for CVE-2026-87736?** A patch was published on 2026-08-07: mirage-crypto-ec 2.3.0 released with fix Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-87736 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-87736?** Check whether you run OCaml Mirage-Crypto-Ec at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is an out-of-bounds read (CWE-125) in the internal Point.of_octets function that fails to validate the length of input buffers for compressed elliptic curve points. The affected functions include Dsa.pub_of_octets and Dh.key_exchange across all NIST curves (P-256, P-384, P-521). An attacker can supply a short buffer as a compressed point, triggering an exception and memory access violation. The fix requires adding proper buffer length validation before processing compressed points. Version 2.3.0 and later include the corrective patch.

## Affected products

- OCaml Mirage-Crypto-EC before 2.3.0

## Timeline

- 2026-07-28: disclosed: Vulnerability reported to security@ocaml.org
- 2026-08-07: patched: mirage-crypto-ec 2.3.0 released with fix
- 2026-08-07: advisory: Security advisory published

## Related threats

- [mirage-crypto-ec timing side channel in NIST elliptic-curve scalar multiplication](https://junglewise.ai/threats/cve-2026-87737-mirage-crypto-ec-timing-side-channel-in-nist-elliptic-curve)
- [Mirage-crypto-ec ECDSA signature forgery via point at infinity](https://junglewise.ai/threats/cve-2026-87733-mirage-crypto-ec-ecdsa-signature-forgery-via-point-at-infinity)