# CVE-2026-54500 — ohler55 oj

> As of 2026-07-01, CVE-2026-54500 is a MEDIUM-severity vulnerability in ohler55 oj, CVSS v3.1 5.3, EPSS 0.1% (8.7th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-54500, most recently “GitLab RCE via Chained Oj JSON Parser Memory-Safety Flaws (Code Execution as 'git' User)”.

**Last updated:** 2026-07-01

## What is CVE-2026-54500?

Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. In versions prior to 3.17.3, Oj.load in :object mode reads uninitialized stack memory (and, for long keys, reads out of bounds) when parsing a JSON object whose key is 254 bytes or longer. The interned bytes can surface to the caller, disclosing process stack memory. In ext/oj/intern.c, form_attr() handles the long-key path by allocating a heap buffer, `b`, populating it with the attribute name, and then freeing it — but it passed the uninitialized stack buffer buf (not b) to rb_intern3(). rb_intern3 therefore reads len + 1 bytes of uninitialized stack memory. When the key length is >= 256, it also reads out of bounds past the 256-byte buf. The resulting bytes are interned and can reach the caller via the produced Symbol or via the EncodingError message raised on invalid UTF-8, leaking process stack contents. This issue has been fixed in version 3.17.3.

The record classifies CVE-2026-54500 under weakness classes [CWE-125](https://intel.threadlinqs.com/cwe/CWE-125), [CWE-908](https://intel.threadlinqs.com/cwe/CWE-908). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 120 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 5.3 — MEDIUM (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **EPSS (FIRST):** 0.1% probability of exploitation in the next 30 days, higher than 8.7% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-06-30, last modified 2026-07-01

## Is CVE-2026-54500 being exploited?

It currently carries a trending score of 12 in the Threadlinqs vulnerability feed.

## Affected products and versions

- **ohler55**: oj

## How to fix CVE-2026-54500

No vendor patch reference has been recorded for CVE-2026-54500 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-54500

1 tracked threat in the Threadlinqs corpus references CVE-2026-54500, either in the campaign’s CVE list or as an indicator on the campaign record.

- [GitLab RCE via Chained Oj JSON Parser Memory-Safety Flaws (Code Execution as 'git' User)](https://intel.threadlinqs.com/threat/TL-2026-1691) — HIGH · 2026-07-25

## Sources

Enriched from CVE.org, NVD, FIRST EPSS. Last verified by Threadlinqs on 2026-10-10. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com](https://github.com/ohler55/oj/security/advisories/GHSA-fm7p-mprw-wjm9)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-54500
Full detection coverage and IOCs for threats exploiting CVE-2026-54500 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp