CVE-2026-54903

What it is

Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. In versions prior to 3.17.2, Oj.load is vulnerable to heap corruption when parsing a JSON string longer than 2 GB. An integer overflow in buf_append_string (buf.h:61) converts the string length to a large negative size_t, causing memcpy to copy an astronomically large amount of data out of bounds. This crashes the process and can corrupt adjacent heap memory. The issue has been fixed in version 3.17.2.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-07-01 00:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-25 17:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.4% in the next 30 days (EPSS).
• Severity: 6.3 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-07-01 00:16 UTC

Last modified

2026-10-25 17:10 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-190 · Integer overflow

Record status

Deferred

Attack profile CVSS 4.0 · 6.3

Attack vector

Network

Complexity

Low

Attack requirements

Present

Privileges needed

None

User interaction

None

Confidentiality

None

Integrity

None

Availability

Low

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-54903.md and follow it. Check whether this project is affected by CVE-2026-54903. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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