CVE catalog
CVE-2026-54911
UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.13.0, ujson.dumps() (or ujson.dump() or ujson.encode()) have a reject_bytes=False option. When
- Severity
- Medium · CVSS 6.5
- Published
- Source
- [NVD] · [CVE record]
- EPSS
- 0.37% · Oct 25, 2026
UltraJSON is a fast JSON encoder and decoder written in pure C with bindings for Python 3.7+. Prior to 5.13.0, ujson.dumps() (or ujson.dump() or ujson.encode()) have a reject_bytes=False option. When set, they may accept malformed or truncated UTF-8 byte sequences, silently rewriting them into different Unicode characters instead of rejecting them. This leads to input validation bypass and data integrity issues. This vulnerability is fixed in 5.13.0.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | ujson | sid | 5.13.0-1 | fixed |
| Debian | ujson | forky | 5.13.0-1 | fixed |
| Debian | ujson | trixie | 5.10.0-1 | vulnerable |
| Debian | ujson | bookworm | 5.7.0-1 | vulnerable |
| Cpe | ujson | Not reported | Not reported | vulnerable |
| Cpe | ultrajson | Not reported | 5.13.0 | fixed |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | ujson | source | sid | 5.13.0-1 | not yet assigned | Not reported | [1140630] |
| Debian | ujson | source | forky | 5.13.0-1 | not yet assigned | Not reported | [1140630] |
| Debian | ujson | source | trixie | (unfixed) | not yet assigned | Not reported | [1140630] |
| Debian | ujson | source | bookworm | (unfixed) | not yet assigned | Not reported | [1140630] |
| Cpe | ultrajson | cpe | Not reported | 5.13.0 | Not reported | Not reported | Not reported |
Notes
[trixie] ujson: Minor issue [bookworm] ujson: Minor issue
OpenFactory catalog packages
[Debian 12 (Bookworm)]
- [python3-ujson]Affected
Source package: [ujson]
Details (2)
5.7.0-1· amd64 · bookwormAffected
nvd · ujson · debian · bookworm; nvd · ujson · debian · 12
5.7.0-1· arm64 · bookwormAffected
nvd · ujson · debian · bookworm; nvd · ujson · debian · 12
[Debian 13 (Trixie)]
- [python3-ujson]Affected
Source package: [ujson]
Details (2)
5.10.0-1+b4· amd64 · trixieAffected
nvd · ujson · debian · 13
5.10.0-1+b4· arm64 · trixieAffected
nvd · ujson · debian · 13
Observed:
References
- [https://nvd.nist.gov/vuln/detail/CVE-2026-54911]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2026-54911]
- [https://security-tracker.debian.org/tracker/CVE-2026-54911]
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-54911.json]
[Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX]