CVE-2026-54900

MEDIUMPre-NVD 6.36.3—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 83% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Trending — 3 sources updated this week
6.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 6.3Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. In versions prior to 3.17.2, when in usual mode with create_id enabled, Oj::Parser#parse is vulnerable to heap corruption via a negative-size memcpy. When a JSON object key is exactly 65,535 bytes long, an integer truncation in form_attr (usual.c:63) converts the length to -1 before passing it to memcpy. This causes memcpy to copy SIZE_MAX bytes (interpreted as a huge size_t), corrupting heap memory and crashing the process. The issue has been fixed in version 3.17.2.

CVSS v3
6.3
EG Score
6.3(medium)
EPSS
16.6%
KEV
Not listed

Published

June 19, 2026

Last Modified

July 1, 2026

Advisory Details (1)

Auto-updated Jul 1, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

DFVULN-854: Negative-Size memcpy in Oj::Parser create_id Attribute Handling · Advisory · ohler55/oj · GitHub

https://github.com/ohler55/oj/security/advisories/GHSA-9cv6-qcjw-4grx

Vendor Advisories for CVE-2026-54900(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
RubyGems(1)
PackageVulnerable rangeFixed inDependents
oj0.5 ... 3.9.2 (294 versions)3.17.3—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 16× in last 7d / 17× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-06 16:27 UTCEPSS rescore
  2. 2026-07-06 16:27 UTCEPSS rescore
  3. 2026-07-06 12:15 UTCEG score recompute
  4. 2026-07-06 02:23 UTCEPSS rescore
  5. 2026-07-06 02:23 UTCEPSS rescore
  6. 2026-07-05 09:57 UTCEG score recompute
  7. 2026-07-05 02:31 UTCEPSS rescore
  8. 2026-07-05 02:30 UTCEPSS rescore
  9. 2026-07-04 07:49 UTCEG score recompute
  10. 2026-07-04 06:31 UTCEPSS rescore
  11. 2026-07-04 06:31 UTCEPSS rescore
  12. 2026-07-03 05:35 UTCEG score recompute
  13. 2026-07-02 03:28 UTCEG score recompute
  14. 2026-07-01 15:07 UTCEPSS rescore
  15. 2026-07-01 01:24 UTCEG score recompute▲ 6.30
  16. 2026-07-01 01:19 UTCNVD updateCVSS v3 → 6.3 · CVSS v4 → 6.3 · severity → MEDIUM
  17. 2026-06-19 21:24 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-54900?
CVE-2026-54900 is a medium vulnerability published on June 19, 2026. Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. In versions prior to 3.17.2, when in usual mode with createid enabled, Oj::Parser#parse is vulnerable to heap corruption via a negative-size memcpy. When a JSON object key is exactly 65,535 bytes long, an integer…
When was CVE-2026-54900 disclosed?
CVE-2026-54900 was first published in the National Vulnerability Database on June 19, 2026, with the most recent update on July 1, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-54900 actively exploited?
CVE-2026-54900 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 16.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-54900?
CVE-2026-54900 has a CVSS v3 base score of 6.3 (NVD).
How do I remediate CVE-2026-54900?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-54900, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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