CVE-2026-5751

MEDIUMPre-NVD 6.16.1—
EchelonGraph scoreMEDIUM confidence

Score 6.1 from GitHub Security Advisory published 2026-08-23. A secondary CVSS source baseline 6.1; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this week
6.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.3%CVSS: 6.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

justhtml versions 1.13.0 and earlier contain a parser-differential / mutation cross-site scripting (mXSS) vulnerability when using a custom SanitizationPolicy that preserves foreign namespaces (e.g., drop_foreign_namespaces=False with allowlisted SVG/MathML elements or raw-text containers such as ). Specially crafted input can sanitize into markup that appears safe but becomes unsafe when re-parsed by a browser or another HTML parser, allowing markup injection. The default safe configuration (sanitize=True) is not affected. Fixed in 1.14.0.

CVSS v3
6.1
EG Score
6.1MEDIUMmedium confidence
EG Risk
28
EG Risk 28/100CISA SSVC

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
Severity61% × 45%
Exploitation0% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.3%
EPSS %ILE
16th
KEV
Not listed

CISA SSVCTrack at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 23, 2026

Last Modified

August 26, 2026

Advisory Details (2)

Auto-updated Aug 23, 2026
Patch available. Sources: github.
generic

justhtml before 1.14.0 Mutation XSS via custom sanitization policies | Advisories | VulnCheck

https://www.vulncheck.com/advisories/justhtml-before-mutation-xss-via-custom-sanitization-policies
githubMentions a patch (unverified)

Mutation XSS with custom foreign-namespace sanitization policies · Advisory · EmilStenstrom/justhtml · GitHub

https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-r758-8hxw-4845

Vendor Advisories for CVE-2026-5751(1)

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

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFix by version rangeDependents
justhtml1.13.0
  • 1.13.0 up to 1.14.0: fixed in 1.14.0
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 21× in last 7d / 80× 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 130 total refreshes for this CVE.

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

Related CVEs(same product + same CWE)

Frequently asked(5)

What is CVE-2026-5751?
CVE-2026-5751 is a medium vulnerability published on August 23, 2026. justhtml versions 1.13.0 and earlier contain a parser-differential / mutation cross-site scripting (mXSS) vulnerability when using a custom SanitizationPolicy that preserves foreign namespaces (e.g., dropforeignnamespaces=False with allowlisted SVG/MathML elements or raw-text containers such as…
When was CVE-2026-5751 disclosed?
CVE-2026-5751 was first published on August 23, 2026, with the most recent update on August 26, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-5751 actively exploited?
CVE-2026-5751 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.3% probability of exploitation in the next 30 days (16th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-5751?
CVE-2026-5751 has a CVSS base score of 6.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-5751?
A fix for CVE-2026-5751 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-5751 are linked in the Vendor Advisories panel on this page.

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