CVE-2026-44660 — Security Box Score

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Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-44660HIGH

UltraJSON: Memory Leak in ujson.dump() on Write Failure

  AV  AC  AT  PR  UI  VC  VI  VA   CVSS    EPSS   %ile   KEV
   N   L   N   N   N   N   N   H    8.7   .0042   35.3     —

AFFECTED
  Product    Versions    Fixed
  ultrajson  < 5.12.1 –  —

TIMELINE
  May 7   Reserved by GitHub_M
  May 27  EXPLOIT PUBLISHED — CVE-2026-44660 (ultrajson). Public exploit reference added.
  May 27  Published (CNA: GitHub_M)

CWE-401 · CNA: GitHub_M · CVSS v4.0 · 3 references · NVD status: Analyzed

Description

UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.12.1, when ujson.dump() writes to a file-like object and the write operation raises an exception, the serialized JSON string object is not decremented, leaking memory. Each failed write operation leaks the full size of the serialized payload. This vulnerability is fixed in 5.12.1.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
May 7, 2026	Reserved	Reserved by GitHub_M
May 27, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-44660 (ultrajson). Public exploit reference added.
May 27, 2026	Published	Published (CNA: GitHub_M)

Affected

Affected products and packages — 1 row
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
ultrajson	ultrajson	—	< 5.12.1	—

Weaknesses

CWE-401

References (3)

https://github.com/ultrajson/ultrajson/commit/82af1d0ac01d09aa40c887b460d44b9d9f4bccd9 [Patch]
https://github.com/ultrajson/ultrajson/releases/tag/5.12.1 [Product, Release Notes]
https://github.com/ultrajson/ultrajson/security/advisories/GHSA-c38f-wx89-p2xg [Exploit, Mitigation, Patch, Vendor Advisory]

Authoritative record: CVE-2026-44660 at cve.org

Vendors: ultrajson

Weaknesses: CWE-401

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-44660 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.