CVE-2026-54911

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 70% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.5Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
6.5
EG Score
6.5(medium)
EG Risk
44(Track)
EG Risk 44/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity65% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
30%
KEV
Not listed

Published

June 19, 2026

Last Modified

June 26, 2026

Advisory Details (3)

Auto-updated Jun 23, 2026
Patch available. Sources: github, github_commit, github_release.
github_release Patch Available

5.13.0

Patch available: ultrajson/ultrajson 5.13.0

https://github.com/ultrajson/ultrajson/releases/tag/5.13.0
github_commit Patch Available

commit 169eaf36b111 (ultrajson/ultrajson)

Patch available: ultrajson/ultrajson 5.13.0 (contains commit 169eaf36b111)

https://github.com/ultrajson/ultrajson/commit/169eaf36b1116fece5034ee79a7a0ef3f6deedcf
github Patch Available

Malformed/Truncated UTF-8 Accepted and Silently Rewritten in ujson.dumps() · Advisory · ultrajson/ultrajson · GitHub

https://github.com/ultrajson/ultrajson/security/advisories/GHSA-3j69-69wj-xqx2

Vendor Advisories for CVE-2026-54911(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(5 across 5 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
ujson4.0.2-1 ... 5.9.0-1 (17 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
ujson5.10.0-1 ... 5.9.0-1 (8 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
ujson5.10.0-1, 5.11.0-1, 5.11.0-2, 5.11.0-3, 5.13.0-1——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
ujson5.10.0-1, 5.11.0-1, 5.11.0-2, 5.11.0-35.13.0-1—
PyPI(1)
PackageVulnerable rangeFixed inDependents
ujson1.15 ... 5.9.0 (41 versions)5.13.0—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 11× in last 7d / 50× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 101 total refreshes for this CVE.

  1. 2026-08-26 14:46 UTCEPSS rescore
  2. 2026-08-25 13:49 UTCEPSS rescore
  3. 2026-08-25 07:22 UTCEG score recompute
  4. 2026-08-24 05:03 UTCEG score recompute
  5. 2026-08-23 00:19 UTCEPSS rescore
  6. 2026-08-22 23:37 UTCEG score recompute
  7. 2026-08-21 23:49 UTCEPSS rescore
  8. 2026-08-21 11:51 UTCEG score recompute
  9. 2026-08-20 22:55 UTCEPSS rescore
  10. 2026-08-20 09:18 UTCEG score recompute
  11. 2026-08-19 17:04 UTCEPSS rescore
  12. 2026-08-19 07:00 UTCEG score recompute
  13. 2026-08-18 13:48 UTCEPSS rescore
  14. 2026-08-17 13:47 UTCEPSS rescore
  15. 2026-08-16 20:24 UTCEG score recompute
  16. 2026-08-16 14:56 UTCEPSS rescore
  17. 2026-08-16 02:14 UTCEPSS rescore
  18. 2026-08-15 15:30 UTCEG score recompute
  19. 2026-08-15 01:30 UTCEPSS rescore
  20. 2026-08-14 13:12 UTCEG score recompute
  21. 2026-08-13 22:00 UTCEPSS rescore
  22. 2026-08-13 10:55 UTCEG score recompute
  23. 2026-08-12 13:51 UTCEPSS rescore
  24. 2026-08-12 08:38 UTCEG score recompute
  25. 2026-08-11 06:21 UTCEG score recompute
Show 75 more
  1. 2026-08-11 00:00 UTCEPSS rescore
  2. 2026-08-10 04:04 UTCEG score recompute
  3. 2026-08-09 13:46 UTCEPSS rescore
  4. 2026-08-09 01:48 UTCEG score recompute
  5. 2026-08-08 16:37 UTCEPSS rescore
  6. 2026-08-07 23:31 UTCEG score recompute
  7. 2026-08-06 21:14 UTCEG score recompute
  8. 2026-08-06 13:47 UTCEPSS rescore
  9. 2026-08-05 19:17 UTCEPSS rescore
  10. 2026-08-04 16:40 UTCEG score recompute
  11. 2026-08-04 15:10 UTCEPSS rescore
  12. 2026-08-04 10:39 UTCEPSS rescore
  13. 2026-08-03 14:20 UTCEG score recompute
  14. 2026-08-03 10:36 UTCEPSS rescore
  15. 2026-08-02 10:41 UTCEG score recompute
  16. 2026-08-02 02:27 UTCEPSS rescore
  17. 2026-08-01 08:24 UTCEG score recompute
  18. 2026-08-01 04:16 UTCEPSS rescore
  19. 2026-07-31 06:07 UTCEG score recompute
  20. 2026-07-30 16:28 UTCEPSS rescore
  21. 2026-07-30 03:50 UTCEG score recompute
  22. 2026-07-30 01:30 UTCEPSS rescore
  23. 2026-07-29 01:33 UTCEG score recompute
  24. 2026-07-28 15:37 UTCEPSS rescore
  25. 2026-07-27 21:20 UTCEG score recompute
  26. 2026-07-26 16:47 UTCEG score recompute
  27. 2026-07-26 14:54 UTCEPSS rescore
  28. 2026-07-25 14:18 UTCEPSS rescore
  29. 2026-07-24 14:18 UTCEPSS rescore
  30. 2026-07-23 14:18 UTCEPSS rescore
  31. 2026-07-23 03:20 UTCEG score recompute
  32. 2026-07-22 14:08 UTCEPSS rescore
  33. 2026-07-21 15:25 UTCEPSS rescore
  34. 2026-07-20 17:08 UTCEPSS rescore
  35. 2026-07-19 14:31 UTCEPSS rescore
  36. 2026-07-19 14:31 UTCEPSS rescore
  37. 2026-07-19 02:29 UTCEPSS rescore
  38. 2026-07-18 10:04 UTCEPSS rescore
  39. 2026-07-16 17:03 UTCEPSS rescore
  40. 2026-07-15 16:57 UTCEPSS rescore
  41. 2026-07-15 16:57 UTCEPSS rescore
  42. 2026-07-15 02:00 UTCEPSS rescore
  43. 2026-07-15 02:00 UTCEPSS rescore
  44. 2026-07-13 22:31 UTCEPSS rescore
  45. 2026-07-13 06:13 UTCEPSS rescore
  46. 2026-07-13 06:13 UTCEPSS rescore
  47. 2026-07-12 05:46 UTCEPSS rescore
  48. 2026-07-11 08:27 UTCEPSS rescore
  49. 2026-07-11 08:27 UTCEPSS rescore
  50. 2026-07-09 19:10 UTCEPSS rescore
  51. 2026-07-09 19:10 UTCEPSS rescore
  52. 2026-07-08 15:16 UTCEPSS rescore
  53. 2026-07-08 15:16 UTCEPSS rescore
  54. 2026-07-07 13:46 UTCEPSS rescore
  55. 2026-07-07 13:46 UTCEPSS rescore
  56. 2026-07-06 16:27 UTCEPSS rescore
  57. 2026-07-06 16:27 UTCEPSS rescore
  58. 2026-07-06 02:23 UTCEPSS rescore
  59. 2026-07-06 02:23 UTCEPSS rescore
  60. 2026-07-05 02:31 UTCEPSS rescore
  61. 2026-07-05 02:30 UTCEPSS rescore
  62. 2026-07-04 06:31 UTCEPSS rescore
  63. 2026-07-04 06:31 UTCEPSS rescore
  64. 2026-07-01 15:07 UTCEPSS rescore
  65. 2026-06-30 23:22 UTCEPSS rescore
  66. 2026-06-29 14:06 UTCEPSS rescore
  67. 2026-06-29 14:06 UTCEPSS rescore
  68. 2026-06-28 14:07 UTCEPSS rescore
  69. 2026-06-28 04:56 UTCEPSS rescore
  70. 2026-06-28 04:56 UTCEPSS rescore
  71. 2026-06-27 03:08 UTCEPSS rescore
  72. 2026-06-25 13:49 UTCEPSS rescore
  73. 2026-06-24 14:05 UTCEPSS rescore
  74. 2026-06-23 21:33 UTCEPSS rescore
  75. 2026-06-23 21:33 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-54911?
CVE-2026-54911 is a medium vulnerability published on June 19, 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…
When was CVE-2026-54911 disclosed?
CVE-2026-54911 was first published in the National Vulnerability Database on June 19, 2026, with the most recent update on June 26, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-54911 actively exploited?
CVE-2026-54911 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 70.0% of all scored CVEs.
What is the CVSS score of CVE-2026-54911?
CVE-2026-54911 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-54911?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-54911, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-54911

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