CVE-2026-28364

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-02-27 · updated 2026-07-15
Weakness: CWE-126

Description

In OCaml before 4.14.3 and 5.x before 5.4.1, a buffer over-read in Marshal deserialization (runtime/intern.c) enables remote code execution through a multi-phase attack chain. The vulnerability stems from missing bounds validation in the readblock() function, which performs unbounded memcpy() operations using attacker-controlled lengths from crafted Marshal data.

Affected products

OCaml: before 4.14.3; from 5.0.0 before 5.4.1 — fixed in 4.14.3, 5.4.1

How to fix

Upgrade to a fixed version: OCaml 4.14.3, 5.4.1. Check the vendor advisory for mitigations.

References

https://github.com/ocaml/security-advisories/blob/generated-osv/2026/OSEC-2026-01.json
https://osv.dev/vulnerability/OSEC-2026-01
https://access.redhat.com/security/cve/CVE-2026-28364
https://bugzilla.redhat.com/show_bug.cgi?id=2443348
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-28364.json

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