Disclosure summary
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.
Source-reported weakness categories
CWE-126
Source-specific records & product guidance
Sources retain their own attribution and scoring. Follow the original record to confirm affected versions, fixed releases, and configuration conditions.
Microsoft Security Updates (CVRF) · 2026-Feb
Open original source · Updated Mar 11, 2026
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.
Maximum of vendor-reported product scores; products and fixed builds are associations, not a universal affected-version statement.
Microsoft maximum product score: 7.9
| Vendor | Product / association | Version / bounds |
|---|---|---|
| Microsoft update guide | azl3 ocaml 5.1.1-1 on Azure Linux 3.0 | (MSRC status code 3) |
| Microsoft update guide | cbl2 ocaml 4.13.1-2 on CBL Mariner 2.0 | (MSRC status code 3) |
Vendor remediation references
- CBL-Mariner Releases · build 5.1.1-2 · product IDs 20930-17084
- Vendor guidance · product IDs 20930-17084
- CBL-Mariner Releases · build 4.13.1-3 · product IDs 21039-17086
- Vendor guidance · product IDs 21039-17086
Original records & references
- NIST NVD record
- CVE Program record
- msrc.microsoft.com — Vendor advisory
PUBLISHED 2026-02-27T20:04:48-05:00
MODIFIED 2026-03-11T10:35:49-04:00
INGESTED 2026-10-08T12:45:17-04:00