Predictive Vulnerability Intelligence.

Product

  • Product
  • Pricing
  • Documentation

Company

  • About
  • Partnerships
  • Blog
  • Support

Legal

  • Terms
  • Privacy
  • Data Licensing

© 2026 FAUCET Technologies LLC. All rights reserved.

CVE-2026-54911

24
FAUCET Score

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.

First published: Jun 22, 2026Last modified: Jun 22, 2026

Impacted Technologies

VendorProductVersion(s)CPE
< 5.13.0CPE matchmatch criteria
cpe:2.3:a:ultrajson_project:ultrajson:*:*:*:*:*:python:*:*

CVSS Data

CVSS version used by this source: 3.1

6.5MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
2.5
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.27%
Probability of exploitation in next 30 days
EPSS Percentile
19.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0027 is in the 9th percentile among its peer group of 23,723 CVEs.

Social Chatter

No social media mentions found for this CVE.

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

pippatch availablevia ghsa
Product: ujsonFixed in: 5.13.0

Vendor Advisories (1)

pipGHSA-3j69-69wj-xqx2medium

UltraJSON: Malformed/Truncated UTF-8 Accepted and Silently Rewritten in ujson.dumps()

Jun 19, 2026

References

github.com / ultrajson/ultrajson/commit/169eaf36b1116fece5034ee79a7a0ef3f6deedcf
Patch
github.com / ultrajson/ultrajson/releases/tag/5.13.0
ProductRelease Notes
github.com / ultrajson/ultrajson/security/advisories/GHSA-3j69-69wj-xqx2
MitigationPatchVendor Advisory