UltraJSON has an integer overflow handling large indent leads to buffer overflow or infinite loop

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-32875: 0.48% estimated exploitation activity in the next 30 days; percentile 41.25 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary ujson.dumps() crashes the Python interpreter (segmentation fault) when the product of the indent parameter and the nested depth of the input exceeds INT32MAX. 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. (Note: A negative indent to ujson means add spaces after colons but do not add line breaks or indentation. It is unclear to the current maintainers whether this was ever even an intended feature or just a byproduct of the way it was written.) Exploitability 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. (Even with the fix for this vulnerability, such usage is strongly advised against since even a bug-free…

Published by the source

18 Mar 2026, 13:01 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 13:37 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-c8rr-9gxc-jprv

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-c8rr-9gxc-jprv

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# Patch Next advisory brief: CVE-2026-32875

Advisory: UltraJSON has an integer overflow handling large indent leads to buffer overflow or infinite loop
IDs: CVE-2026-32875, GHSA-c8rr-9gxc-jprv
Record: https://patchnext.com/advisories/cve-2026-32875 (revision 2, source checked 26 Oct 2026, 13:37 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: ujson 5.12.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI ujson: affected >= 5.1.0, <= 5.11.0; fixed in 5.12.0

## Suggested inspection (read-only)
- `python -m pip show ujson`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on ujson.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-c8rr-9gxc-jprv (OSV record GHSA-c8rr-9gxc-jprv lists affected ranges: PyPI ujson >=5.1.0 <5.12.0 (fixed))
- Verified: https://github.com/advisories/GHSA-c8rr-9gxc-jprv (GitHub-reviewed advisory GHSA-c8rr-9gxc-jprv lists affected ranges: PyPI ujson >=5.1.0 <=5.11.0)

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