PyPIPackage

ujson

7 known vulnerabilities (4 high, 2 medium), with the versions each affects and the releases that fix them.

Latest release: 6.1.0 (Nov 3, 2026): no advisory affects it
Newest unaffected release: 6.1.0 (Nov 3, 2026), the latest release
Advisories: 7 · 4 high, 2 medium

Weekly downloads: 6.9M
Dependents: 2,905
Releases: 44 since 1.4.0 (Jun 16, 2011)
Registry: PyPI
Releases read: Nov 8, 2026

Version timeline

CVE-2026-54911
Affects 1.4.0 to 5.12.1 (5.13.0 is outside it)
CVE-2026-44660
Affects 1.4.0 to 5.12.0 (5.12.1 is outside it)
CVE-2026-32875
Affects 5.1.0 to 5.11.0 (5.12.0 is outside it)
CVE-2026-32874
Affects 5.4.0 to 5.11.0 (5.12.0 is outside it)
CVE-2022-31116
Affects 1.4.0 to 5.3.0 (5.4.0 is outside it)
CVE-2022-31117
Affects 1.4.0 to 5.3.0 (5.4.0 is outside it)
CVE-2021-45958
Affects 1.34.0 to 5.1.0 (5.2.0 is outside it)

Every release cve.now has on record, lowest version on the left; each bar is a run of versions an advisory affects.

Advisories 7

CVE-2026-54911Medium 6.5
UltraJSON: Malformed/Truncated UTF-8 Accepted and Silently Rewritten in ujson.dumps()
Affected: fixed in 5.13.0.
Fixed in 5.13.0 (released Jun 14, 2026, 8 days before disclosure).
The latest release, 6.1.0, is not affected.
CVE-2026-44660High 8.7
UltraJSON: Memory Leak in ujson.dump() on Write Failure
Affected: fixed in 5.12.1.
Fixed in 5.12.1 (released May 5, 2026, 22 days before disclosure).
The latest release, 6.1.0, is not affected.
CVE-2026-32875High 7.5
UltraJSON has an integer overflow handling large indent leads to buffer overflow or infinite loop
Affected: from 5.1.0, fixed in 5.12.0.
Fixed in 5.12.0 (released Mar 11, 2026, 9 days before disclosure).
The latest release, 6.1.0, is not affected.
CVE-2026-32874High 7.5
UltraJSON has a Memory Leak parsing large integers allows DoS
Affected: from 5.4.0, fixed in 5.12.0.
Fixed in 5.12.0 (released Mar 11, 2026, 9 days before disclosure).
The latest release, 6.1.0, is not affected.
CVE-2022-31116High 7.5
Incorrect handling of invalid surrogate pair characters in ujson
Affected: fixed in 5.4.0.
Fixed in 5.4.0 (released Jul 2, 2022, 3 days before disclosure).
The latest release, 6.1.0, is not affected.
CVE-2022-31117Medium 5.9
Double free of buffer during string decoding in ujson
Affected: fixed in 5.4.0.
Fixed in 5.4.0 (released Jul 2, 2022, 3 days before disclosure).
The latest release, 6.1.0, is not affected.
CVE-2021-45958Unrated
UltraJSON (aka ujson) through 5.1.0 has a stack-based buffer overflow in Buffer_AppendIndentUnchecked (called from encode).
Affected: from 1.34, fixed in 5.2.0; from 4.0.2, fixed in 5.1.0.
Fixed in 5.2.0 (released Apr 5, 2022, 95 days after disclosure).
The latest release, 6.1.0, is not affected.