# CVE-2026-32875: ujson: UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+

CVE-2026-32875 is fixed in 2 products on 1 platform, first by python3-ujson 5.1.0-1ubuntu0.1~esm2, released March 19, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-32875
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0049
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 19, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | python3-ujson Ubuntu 22.04.1 LTS (jammy) | 5.1.0-1ubuntu0.1~esm2 | [python3-ujson 5.1.0-1ubuntu0.1~esm2](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-python3-ujson-5.1.0-1ubuntu0.1-esm2.md) | Mar 19, 2026 |
| Linux | python3-ujson Ubuntu 24.04.5 LTS (noble) | 5.9.0-1ubuntu0.1~esm1 | [python3-ujson 5.9.0-1ubuntu0.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-python3-ujson-5.9.0-1ubuntu0.1-esm1.md) | Mar 19, 2026 |
| Linux | python3-ujson Ubuntu 25.10 (questing) | 5.10.0-1ubuntu0.1 | [python3-ujson 5.10.0-1ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-questing-python3-ujson-5.10.0-1ubuntu0.1.md) | Mar 19, 2026 |
| Linux | python3-ujson Ubuntu 26.04.1 LTS (resolute) | 5.11.0-3ubuntu0.1 | [python3-ujson 5.11.0-3ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-python3-ujson-5.11.0-3ubuntu0.1.md) | Mar 19, 2026 |
| Linux | ujson Debian 14 | 5.13.0-1 | [DEBIAN-CVE-2026-32875](https://patchblox.com/security/data/fix/linux/debian-cve-2026-32875.md) | Mar 20, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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