Vulnerability · Published Mar 20, 2026 · Assigned by GitHub_M
CVE-2026-32875UltraJSON has an integer overflow handling large indent leads to buffer overflow or infinite loop
High 7.5
In plain English
A high-severity integer overflow in ultrajson from ultrajson. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 42% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.23 | py3-ujson | 5.12.0-r0 | ALPINE-CVE-2026-32875 |
| Alpine:v3.24 | py3-ujson | 5.12.0-r0 | ALPINE-CVE-2026-32875 |
| Debian:12 | ujson | no fix listed | DEBIAN-CVE-2026-32875 |
| Debian:13 | ujson | no fix listed | DEBIAN-CVE-2026-32875 |
| Debian:14 | ujson | 5.13.0-1 | DEBIAN-CVE-2026-32875 |
| PyPI | ujson | 5.12.0 | PYSEC-2026-2292 |
| PyPI | ujson | 5.12.0 | GHSA-c8rr-9gxc-jprv |
| Ubuntu:25.10 | ujson | 5.10.0-1ubuntu0.1 | UBUNTU-CVE-2026-32875 |
| Ubuntu:26.04:LTS | ujson | 5.11.0-3ubuntu0.1 | UBUNTU-CVE-2026-32875 |
| Ubuntu:26.10 | ujson | no fix listed | UBUNTU-CVE-2026-32875 |
Affected products (as reported)
Weakness: CWE-190, CWE-787, CWE-835 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- https://github.com/ultrajson/ultrajson/security/advisories/GHSA-c8rr-9gxc-jprv x_refsource_CONFIRM
- https://github.com/ultrajson/ultrajson/issues/700 x_refsource_MISC
- https://github.com/ultrajson/ultrajson/commit/486bd4553dc471a1de11613bc7347a6b318e37ea x_refsource_MISC
- https://access.redhat.com/security/cve/CVE-2026-32875 vdb-entry, x_refsource_REDHAT
- RHBZ#2449400 issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-32875.json x_sadp-csaf-vex