Medium severity6.5NVD Advisory· Published Jun 22, 2026· Updated Jun 26, 2026
CVE-2026-54911
CVE-2026-54911
Description
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.
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
ujsonPyPI | < 5.13.0 | 5.13.0 |
Affected products
26- osv-coords24 versionspkg:apk/chainguard/datahub-ingestionpkg:apk/chainguard/openstack-glance-2025.1pkg:apk/chainguard/openstack-glance-2025.1-fipspkg:apk/chainguard/openstack-glance-2025.2pkg:apk/chainguard/openstack-glance-2025.2-fipspkg:apk/chainguard/openstack-glance-2026.1-fipspkg:apk/chainguard/openstack-horizon-2025.1pkg:apk/chainguard/openstack-horizon-2025.1-fipspkg:apk/chainguard/openstack-horizon-2025.2pkg:apk/chainguard/openstack-horizon-2025.2-fipspkg:apk/chainguard/openstack-horizon-2026.1pkg:apk/chainguard/openstack-horizon-2026.1-fipspkg:apk/chainguard/openstack-keystone-2025.1pkg:apk/chainguard/openstack-keystone-2025.1-fipspkg:apk/chainguard/openstack-keystone-2025.2pkg:apk/chainguard/openstack-keystone-2025.2-fipspkg:apk/chainguard/openstack-keystone-2026.1pkg:apk/chainguard/openstack-keystone-2026.1-fipspkg:apk/chainguard/openstack-placement-2025.1pkg:apk/chainguard/openstack-placement-2025.1-fipspkg:apk/chainguard/openstack-placement-2025.2pkg:apk/chainguard/openstack-placement-2025.2-fipspkg:apk/chainguard/openstack-placement-2026.1pkg:apk/chainguard/openstack-placement-2026.1-fips
< 1.6.0-r4+ 23 more
- (no CPE)range: < 1.6.0-r4
- (no CPE)range: < 30.2.0_git20260616-r5
- (no CPE)range: < 30.2.0_git20260617-r2
- (no CPE)range: < 31.1.0_git20260617-r4
- (no CPE)range: < 31.1.0_git20260617-r3
- (no CPE)range: < 32.0.0_git20260617-r4
- (no CPE)range: < 25.3.2_git20260617-r3
- (no CPE)range: < 25.3.2_git20260617-r2
- (no CPE)range: < 25.5.2_git20260617-r3
- (no CPE)range: < 25.5.2_git20260617-r3
- (no CPE)range: < 25.7.3_git20260624-r2
- (no CPE)range: < 25.7.3_git20260617-r2
- (no CPE)range: < 27.0.1_git20260618-r5
- (no CPE)range: < 27.0.1_git20260618-r5
- (no CPE)range: < 28.0.1_git20260618-r4
- (no CPE)range: < 28.0.1_git20260618-r2
- (no CPE)range: < 29.0.1_git20260616-r5
- (no CPE)range: < 29.0.1_git20260617-r3
- (no CPE)range: < 13.0.0_git20260617-r4
- (no CPE)range: < 13.0.0_git20260617-r3
- (no CPE)range: < 14.0.0_git20260617-r4
- (no CPE)range: < 14.0.0_git20260309-r3
- (no CPE)range: < 15.0.0_git20260617-r4
- (no CPE)range: < 15.0.0_git20260617-r2
Patches
Vulnerability mechanics
References
6- github.com/ultrajson/ultrajson/commit/169eaf36b1116fece5034ee79a7a0ef3f6deedcfnvdPatchWEB
- github.com/ultrajson/ultrajson/security/advisories/GHSA-3j69-69wj-xqx2nvdMitigationPatchVendor AdvisoryWEB
- github.com/advisories/GHSA-3j69-69wj-xqx2ghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-54911ghsaADVISORY
- github.com/pypa/advisory-database/tree/main/vulns/ujson/PYSEC-2026-2294.yamlghsaWEB
- github.com/ultrajson/ultrajson/releases/tag/5.13.0nvdProductRelease NotesWEB
News mentions
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