CVE-2026-5389

MEDIUMPre-NVD 6.16.1—
EchelonGraph scoreHIGH 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 weekElevated
6.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.1Exploit: Elevated riskExposed: 0

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

justhtml versions before 1.13.0 contain a cross-site scripting vulnerability in the to_markdown() function when serializing attacker-controlled pre content. Attackers can place backticks inside sanitized pre elements to break out of fixed-length code fences, allowing raw HTML to execute when the generated Markdown is rendered by CommonMark or GFM-style renderers.

CVSS v3
6.1
EG Score
6.1(high)
EG Risk
43(Track)
EG Risk 43/100SSVC: 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
Severity61% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
9%
KEV
Not listed

Published

August 23, 2026

Last Modified

August 26, 2026

Advisory Details (2)

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

justhtml before 1.13.0 XSS via code fence breakout | Advisories | VulnCheck

https://www.vulncheck.com/advisories/justhtml-before-xss-via-code-fence-breakout
github Patch Available

to_markdown() XSS via code fence breakout in <pre> content · Advisory · EmilStenstrom/justhtml · GitHub

https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-5vp3-3cg6-2rq3

Vendor Advisories for CVE-2026-5389(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 rangeFixed inDependents
justhtml0.1.0 ... 1.9.1 (57 versions)1.13.0—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 18× in last 7d / 75× 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.

  1. 2026-09-18 23:53 UTCEG score recompute
  2. 2026-09-18 23:53 UTCGHSA enrichment
  3. 2026-09-18 19:28 UTCEPSS rescore
  4. 2026-09-17 21:46 UTCEG score recompute
  5. 2026-09-17 21:46 UTCGHSA enrichment
  6. 2026-09-17 19:31 UTCEPSS rescore
  7. 2026-09-16 19:39 UTCEG score recompute
  8. 2026-09-16 19:39 UTCGHSA enrichment
  9. 2026-09-16 14:08 UTCEPSS rescore
  10. 2026-09-16 05:15 UTCEPSS rescore
  11. 2026-09-15 14:14 UTCEG score recompute
  12. 2026-09-15 14:14 UTCGHSA enrichment
  13. 2026-09-15 03:11 UTCEPSS rescore
  14. 2026-09-14 12:08 UTCEG score recompute
  15. 2026-09-14 12:08 UTCGHSA enrichment
  16. 2026-09-13 16:47 UTCEPSS rescore
  17. 2026-09-13 10:02 UTCEG score recompute
  18. 2026-09-13 10:02 UTCGHSA enrichment
  19. 2026-09-12 07:56 UTCEG score recompute
  20. 2026-09-12 07:56 UTCGHSA enrichment
  21. 2026-09-11 14:53 UTCEPSS rescore
  22. 2026-09-11 05:49 UTCEG score recompute
  23. 2026-09-11 05:49 UTCGHSA enrichment
  24. 2026-09-10 09:35 UTCEPSS rescore
  25. 2026-09-10 03:42 UTCGHSA enrichment
Show 50 more
  1. 2026-09-09 01:36 UTCEG score recompute
  2. 2026-09-09 01:36 UTCGHSA enrichment
  3. 2026-09-08 22:01 UTCEPSS rescore
  4. 2026-09-07 19:41 UTCEG score recompute
  5. 2026-09-07 19:41 UTCGHSA enrichment
  6. 2026-09-07 16:01 UTCEPSS rescore
  7. 2026-09-06 17:35 UTCEG score recompute
  8. 2026-09-06 17:35 UTCGHSA enrichment
  9. 2026-09-06 13:47 UTCEPSS rescore
  10. 2026-09-05 15:28 UTCEG score recompute
  11. 2026-09-05 15:28 UTCGHSA enrichment
  12. 2026-09-04 13:20 UTCEG score recompute
  13. 2026-09-04 13:20 UTCGHSA enrichment
  14. 2026-09-04 05:07 UTCEPSS rescore
  15. 2026-09-03 11:11 UTCEG score recompute
  16. 2026-09-03 11:11 UTCGHSA enrichment
  17. 2026-09-02 14:12 UTCEPSS rescore
  18. 2026-09-02 09:02 UTCEG score recompute
  19. 2026-09-02 09:02 UTCGHSA enrichment
  20. 2026-09-01 13:54 UTCEPSS rescore
  21. 2026-09-01 06:52 UTCEG score recompute
  22. 2026-09-01 06:52 UTCGHSA enrichment
  23. 2026-09-01 04:40 UTCEPSS rescore
  24. 2026-08-31 04:45 UTCEG score recompute
  25. 2026-08-31 04:45 UTCGHSA enrichment
  26. 2026-08-30 19:17 UTCEPSS rescore
  27. 2026-08-30 02:38 UTCEG score recompute
  28. 2026-08-30 02:38 UTCGHSA enrichment
  29. 2026-08-30 01:22 UTCEPSS rescore
  30. 2026-08-29 00:32 UTCEG score recompute
  31. 2026-08-29 00:31 UTCGHSA enrichment
  32. 2026-08-28 21:42 UTCEPSS rescore
  33. 2026-08-27 19:31 UTCEG score recompute
  34. 2026-08-27 19:31 UTCGHSA enrichment
  35. 2026-08-27 14:25 UTCEPSS rescore
  36. 2026-08-26 17:25 UTCEG score recompute
  37. 2026-08-26 17:25 UTCGHSA enrichment
  38. 2026-08-26 14:46 UTCEPSS rescore
  39. 2026-08-25 21:41 UTCEG score recompute
  40. 2026-08-25 21:41 UTCGHSA enrichment
  41. 2026-08-25 13:49 UTCEPSS rescore
  42. 2026-08-24 19:25 UTCEG score recompute
  43. 2026-08-24 19:25 UTCGHSA enrichment
  44. 2026-08-24 18:31 UTCEG score recompute
  45. 2026-08-24 18:31 UTCGHSA enrichment
  46. 2026-08-24 16:56 UTCEG score recompute
  47. 2026-08-24 16:55 UTCGHSA enrichment
  48. 2026-08-23 14:20 UTCEG score recompute
  49. 2026-08-23 13:51 UTCEG score recompute
  50. 2026-08-23 13:50 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-5389?
CVE-2026-5389 is a medium vulnerability published on August 23, 2026. justhtml versions before 1.13.0 contain a cross-site scripting vulnerability in the to_markdown() function when serializing attacker-controlled pre content. Attackers can place backticks inside sanitized pre elements to break out of fixed-length code fences, allowing raw HTML to execute when the…
When was CVE-2026-5389 disclosed?
CVE-2026-5389 was first published in the National Vulnerability Database 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-2026-5389 actively exploited?
CVE-2026-5389 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 91.3% of all scored CVEs.
What is the CVSS score of CVE-2026-5389?
CVE-2026-5389 has a CVSS v3 base score of 6.1 (NVD).
How do I remediate CVE-2026-5389?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-5389, 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-2026-5389

Explore →

Is Your Infrastructure Affected by CVE-2026-5389?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs