# ujson (PyPI) vulnerabilities

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

## At a glance

- Latest release: 6.1.0 (Nov 3, 2026): no advisory affects it
- Newest unaffected release: 6.1.0 (Nov 3, 2026), the latest release
- Weekly downloads: 6.9M
- Dependents: 2,905
- Releases: 44 since 1.4.0 (Jun 16, 2011)
- Registry: https://pypi.org/project/ujson/
- Releases read: Nov 8, 2026

## Version timeline

Affected versions per advisory, in version order:

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

## Advisories (7)

### [CVE-2026-54911](https://cve.now/CVE-2026-54911): UltraJSON: Malformed/Truncated UTF-8 Accepted and Silently Rewritten in ujson.dumps()

- Severity: Medium 6.5
- Published: Jun 22, 2026
- 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-2026-44660](https://cve.now/CVE-2026-44660): UltraJSON: Memory Leak in ujson.dump() on Write Failure

- Severity: High 8.7
- Published: May 27, 2026
- 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-2026-32875](https://cve.now/CVE-2026-32875): UltraJSON has an integer overflow handling large indent leads to buffer overflow or infinite loop

- Severity: High 7.5
- Published: Mar 20, 2026
- 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-2026-32874](https://cve.now/CVE-2026-32874): UltraJSON has a Memory Leak parsing large integers allows DoS

- Severity: High 7.5
- Published: Mar 20, 2026
- 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-2022-31116](https://cve.now/CVE-2022-31116): Incorrect handling of invalid surrogate pair characters in ujson

- Severity: High 7.5
- Published: Jul 5, 2022
- 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-2022-31117](https://cve.now/CVE-2022-31117): Double free of buffer during string decoding in ujson

- Severity: Medium 5.9
- Published: Jul 5, 2022
- 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-2021-45958](https://cve.now/CVE-2021-45958): UltraJSON (aka ujson) through 5.1.0 has a stack-based buffer overflow in Buffer\_AppendIndentUnchecked (called from encode).

- Severity: Unrated
- Published: Dec 31, 2021
- 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.

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