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Fencer Vulns
high 7.9

CVE-2026-28364 json

Buffer Over-Read in OCaml Marshal Deserialization

published 2026-02-17 8 mo ago modified 2026-11-06 2 d ago also EUVD-2026-8988 , GHSA-j26j-m5xr-g23c , GHSA-m34r-cgq7-jhfm , OSEC-2026-01 , OSEC-2026-18 , OSEC-2026-23

cvss
7.9
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 15%
public exploits
0
none known

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.

Patch / fix

  • opam ocaml 4.14.3, 4.14.4, 4.14.5, 5.4.1, 5.5.1, 5.5.2
  • OCaml OCaml 4.14.3, 5.4.1
  • ocaml Debian 14 5.4.1-1

debian advisories DEBIAN-CVE-2026-28364

  • ocaml SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Module for Development Tools 15 SP7 +1 more 4.14.2-150600.3.3.1
  • ocaml SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES 15 SP5-LTSS +5 more 4.05.0-150200.15.3.1

suse advisories SUSE-SU-2026:0830-1SUSE-SU-2026:0800-1

  • ocaml openSUSE Tumbleweed 4.14.4-1.1
  • ocaml openSUSE Leap 16.0 4.14.2-160000.4.1

opensuse advisories openSUSE-SU-2026:11136-1openSUSE-SU-2026:20368-1

  • ocaml Azure Linux 3.0 5.1.1-2

azure linux advisories AZL-78495

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-28364 updated cvss 7.9

ocaml: OCaml: Remote code execution via buffer over-read in Marshal deserialization

  • Red Hat Enterprise Linux 6 ocaml, ocaml-x11, ocaml-emacs, ocaml-camlp4, ocaml-labltk, ocaml-source, +2 more
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 ocaml, ocaml-x11, ocaml-emacs, ocaml-camlp4, ocaml-labltk, ocaml-source, +3 more Red Hat Enterprise Linux 8 ocaml, ocaml-camlp4, ocaml-labltk, ocaml-runtime, ocaml-ocamldoc, ocaml-compiler-libs Red Hat Enterprise Linux 9 ocaml, ocaml-labltk, ocaml-source, ocaml-runtime, ocaml-ocamldoc, ocaml-compiler-libs
    affected: no fix planned “Will not fix”
  • Red Hat Enterprise Linux 10 ocaml
    affected: no fix available
  • Red Hat Hardened Images ocaml
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
8 mo ago

Exploit prediction

0.24% chance of exploitation in the next 30 days, higher than 15% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.9 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
CISA ADP 3.1 7.9 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
OSV 3.1 6.8 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

Affected packages

ecosystem package affected fixed in
opam ocaml
<4.14.3
>=5, <5.4.1
<4.14.4
>=5, <5.5.1
<4.14.5
>=5, <5.5.2
4.14.3
5.4.1
4.14.4
5.5.1
4.14.5
5.5.2

Affected products

  • OCaml OCaml
  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 6
  • Red Hat Red Hat Enterprise Linux 7
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat Hardened Images

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.