CVE-2026-32874

HighCVSS 7.5

Published: 20/03/2026(UTC)Updated: 15/07/2026(UTC)Translated: 16/07/2026(UTC)NVD NIST

Exploitation Probability (EPSS)

Low risk

0.48%

38th percentile - higher than 38% of all known CVEs

Summary

UltraJSON versions 5.4.0 through 5.11.0 have a memory leak when parsing large integers outside the range [-2^63, 2^64-1]. The leak copies the string form of the integer plus a NULL byte, potentially leading to memory exhaustion and DoS attacks.

Risk Assessment

The organization is vulnerable to denial of service (DoS) attacks by sending malicious JSON payloads with large integers, which can exhaust server memory and disrupt services.

Recommendation

Immediately upgrade UltraJSON to version 5.12.0 or later. If upgrade is not possible, limit the size of processed JSON data and apply input filtering.

Other vulnerabilities in UltraJSON

CVE-2026-32875High
UltraJSON versions 5.10 through 5.11.0 are vulnerable to buffer overflow or infinite loop via large indent handling. ujson.dumps() crashes the Python interpreter (segmentation fault) when the product of the indent parameter and nested depth exceeds INT32_MAX, or may get stuck in an infinite loop if indent is a large negative number. Both are caused by integer overflow/underflow during memory calculation for indentation and can lead to denial of service.

Original NVD description (English source)

UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Versions 5.4.0 through 5.11.0 contain an accumulating memory leak in JSON parsing large (outside of the range [-2^63, 2^64 - 1]) integers. The leaked memory is a copy of the string form of the integer plus an additional NULL byte. The leak occurs irrespective of whether the integer parses successfully or is rejected due to having more than sys.get_int_max_str_digits() digits, meaning that any sized leak per malicious JSON can be achieved provided that there is no limit on the overall size of the payload. Any service that calls ujson.load()/ujson.loads()/ujson.decode() on untrusted inputs is affected and vulnerable to denial of service attacks. This issue has been fixed in version 5.12.0.