Integer Overflow or Wraparound Affecting py3-ujson package, versions <5.12.0-r0


Severity

Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.07% (22nd percentile)

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications

Snyk Learn

Learn about Integer Overflow or Wraparound vulnerabilities in an interactive lesson.

Start learning
  • Snyk IDSNYK-ALPINE323-PY3UJSON-16322646
  • published30 Apr 2026
  • disclosed20 Mar 2026

Introduced: 20 Mar 2026

CVE-2026-32875  (opens in a new tab)
CWE-190  (opens in a new tab)
CWE-787  (opens in a new tab)
CWE-835  (opens in a new tab)

How to fix?

Upgrade Alpine:3.23 py3-ujson to version 5.12.0-r0 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream py3-ujson package and not the py3-ujson package as distributed by Alpine. See How to fix? for Alpine:3.23 relevant fixed versions and status.

UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Versions 5.10 through 5.11.0 are vulnerable to buffer overflow or infinite loop through large indent handling. ujson.dumps() crashes the Python interpreter (segmentation fault) when the product of the indent parameter and the nested depth of the input exceeds INT32_MAX. It can also get stuck in an infinite loop if the indent is a large negative number. Both are caused by an integer overflow/underflow whilst calculating how much memory to reserve for indentation. And both can be used to achieve denial of service. To be vulnerable, a service must call ujson.dump()/ujson.dumps()/ujson.encode() whilst giving untrusted users control over the indent parameter and not restrict that indentation to reasonably small non-negative values. A service may also be vulnerable to the infinite loop if it uses a fixed negative indent. An underflow always occurs for any negative indent when the input data is at least one level nested but, for small negative indents, the underflow is usually accidentally rectified by another overflow. This issue has been fixed in version 5.12.0.

CVSS Base Scores

version 3.1