CVE-2026-28364: In OCaml before 4.14.3 and 5.x before 5.4.1, a buffer over-read in Marshal deserialization (runtime/intern.c)

Routine

HIGH 7.9UPGRADE

CVE-2026-28364 is a high-severity flaw (CVSS 7.9) affecting ocaml. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	7.9 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 85%)
CISA exploited list	No
Weakness	CWE-126, CWE-125
Published	2026-02-27
Last modified	2026-07-15

Publisher (CNA): MITRE · Vendor: ocaml

Last updated 2026-07-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-02-27 04:16 UTCPublished CVE record published
2026-07-15 02:19 UTCUpdated Record last modified

ocaml ocaml UPGRADE

Affected: < 4.14.3 · >= 5.0.0 and < 5.4.1

Fixed in: 4.14.3, 5.4.1

Safe to downgrade to: a release before 5.0.0

1. Check installed version

apt-cache policy ocaml || rpm -q ocaml || ocaml --version

2. UPGRADE to 4.14.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade ocaml

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade ocaml

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 5.0.0 (Debian / Ubuntu)

apt-cache madison ocaml sudo apt install ocaml=<VERSION_BEFORE_5.0.0> sudo apt-mark hold ocaml

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list ocaml sudo dnf downgrade ocaml-<VERSION_BEFORE_5.0.0> sudo dnf versionlock add ocaml

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-28364?

ocaml: upgrade to 4.14.3, 5.4.1. Exact commands for each OS are on this page.

Is CVE-2026-28364 being exploited?

CVE-2026-28364 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-28364 affect?

CVE-2026-28364 affects ocaml. Severity is high (CVSS 7.9). 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 re

How urgent is CVE-2026-28364?

Priority 31/100. High severity

Related CVEs

CVE-2026-34353 MEDIUM 5.9 UPGRADE In OCaml through 4.14.3, Bigarray.reshape allows an integer overflow, and resultant reading of arbitrary memor

References

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