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.
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Tracking
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Advisories
| Source | ID | Title |
|---|---|---|
Github GHSA |
GHSA-c8rr-9gxc-jprv | UltraJSON has an integer overflow handling large indent leads to buffer overflow or infinite loop |
Fixes
Solution
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Workaround
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References
History
Fri, 20 Mar 2026 02:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | 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. | |
| Title | UltraJSON has an integer overflow handling large indent leads to buffer overflow or infinite loop | |
| Weaknesses | CWE-190 CWE-787 CWE-835 |
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| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-03-20T01:35:23.362Z
Reserved: 2026-03-16T21:03:44.420Z
Link: CVE-2026-32875
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Status : Received
Published: 2026-03-20T02:16:35.887
Modified: 2026-03-20T02:16:35.887
Link: CVE-2026-32875
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OpenCVE Enrichment
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Github GHSA