CVE-2026-5389

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 weekElevated
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: Elevated riskExposed services: Not assessed

A fix is available — apply it.

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
6.1MEDIUMmedium confidence
EG Risk
43
EG Risk 43/100CISA 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%
Exploitation40% × 40%
Automatability0% × 15%
CISA SSVC: Track at low or medium mission impact; Track* at high (mission-essential systems).
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 low or medium mission impact; Track* at high (mission-essential systems).

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

Exploitation public PoC (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 1.13.0 XSS via code fence breakout | Advisories | VulnCheck

https://www.vulncheck.com/advisories/justhtml-before-xss-via-code-fence-breakout
githubMentions a patch (unverified)

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 rangeFix by version rangeDependents
justhtml0.1.0 ... 1.9.1 (57 versions)
  • every version up to 1.13.0: fixed in 1.13.0
—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 16× in last 7d / 74× 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 126 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. 2026-10-08 17:13 UTCEPSS rescore
  6. 2026-10-08 07:19 UTCEG score recompute
  7. 2026-10-08 07:18 UTCGHSA enrichment
  8. 2026-10-07 23:48 UTCEPSS rescore
  9. 2026-10-07 05:05 UTCEG score recompute
  10. 2026-10-07 05:05 UTCGHSA enrichment
  11. 2026-10-06 15:18 UTCEPSS rescore
  12. 2026-10-06 02:58 UTCEG score recompute
  13. 2026-10-06 02:58 UTCGHSA enrichment
  14. 2026-10-05 17:43 UTCEPSS rescore
  15. 2026-10-04 23:22 UTCEPSS rescore
  16. 2026-10-04 20:45 UTCGHSA enrichment
  17. 2026-10-03 16:34 UTCEG score recompute
  18. 2026-10-03 16:34 UTCGHSA enrichment
  19. 2026-10-03 14:26 UTCEPSS rescore
  20. 2026-10-02 17:56 UTCEPSS rescore
  21. 2026-10-02 12:54 UTCEG score recompute
  22. 2026-10-02 12:54 UTCGHSA enrichment
  23. 2026-10-01 19:50 UTCEPSS rescore
  24. 2026-10-01 09:28 UTCEG score recompute
  25. 2026-10-01 09:28 UTCGHSA enrichment
Show 75 more
  1. 2026-09-30 15:03 UTCEPSS rescore
  2. 2026-09-30 07:22 UTCEG score recompute
  3. 2026-09-30 07:22 UTCGHSA enrichment
  4. 2026-09-29 05:10 UTCEG score recompute
  5. 2026-09-29 05:10 UTCGHSA enrichment
  6. 2026-09-28 13:51 UTCEPSS rescore
  7. 2026-09-28 03:04 UTCEG score recompute
  8. 2026-09-28 03:04 UTCGHSA enrichment
  9. 2026-09-27 00:53 UTCEG score recompute
  10. 2026-09-27 00:52 UTCGHSA enrichment
  11. 2026-09-26 15:59 UTCEPSS rescore
  12. 2026-09-25 12:30 UTCEG score recompute
  13. 2026-09-25 12:30 UTCGHSA enrichment
  14. 2026-09-24 14:04 UTCEPSS rescore
  15. 2026-09-24 10:24 UTCEG score recompute
  16. 2026-09-24 10:24 UTCGHSA enrichment
  17. 2026-09-23 17:54 UTCEPSS rescore
  18. 2026-09-23 08:18 UTCEG score recompute
  19. 2026-09-23 08:18 UTCGHSA enrichment
  20. 2026-09-22 06:11 UTCEG score recompute
  21. 2026-09-22 06:11 UTCGHSA enrichment
  22. 2026-09-21 04:06 UTCEG score recompute
  23. 2026-09-21 04:06 UTCGHSA enrichment
  24. 2026-09-20 20:16 UTCEPSS rescore
  25. 2026-09-20 01:59 UTCEG score recompute
  26. 2026-09-20 01:59 UTCGHSA enrichment
  27. 2026-09-18 23:53 UTCEG score recompute
  28. 2026-09-18 23:53 UTCGHSA enrichment
  29. 2026-09-18 19:28 UTCEPSS rescore
  30. 2026-09-17 21:46 UTCEG score recompute
  31. 2026-09-17 21:46 UTCGHSA enrichment
  32. 2026-09-17 19:31 UTCEPSS rescore
  33. 2026-09-16 19:39 UTCEG score recompute
  34. 2026-09-16 19:39 UTCGHSA enrichment
  35. 2026-09-16 14:08 UTCEPSS rescore
  36. 2026-09-16 05:15 UTCEPSS rescore
  37. 2026-09-15 14:14 UTCEG score recompute
  38. 2026-09-15 14:14 UTCGHSA enrichment
  39. 2026-09-15 03:11 UTCEPSS rescore
  40. 2026-09-14 12:08 UTCEG score recompute
  41. 2026-09-14 12:08 UTCGHSA enrichment
  42. 2026-09-13 16:47 UTCEPSS rescore
  43. 2026-09-13 10:02 UTCEG score recompute
  44. 2026-09-13 10:02 UTCGHSA enrichment
  45. 2026-09-12 07:56 UTCEG score recompute
  46. 2026-09-12 07:56 UTCGHSA enrichment
  47. 2026-09-11 14:53 UTCEPSS rescore
  48. 2026-09-11 05:49 UTCEG score recompute
  49. 2026-09-11 05:49 UTCGHSA enrichment
  50. 2026-09-10 09:35 UTCEPSS rescore
  51. 2026-09-10 03:42 UTCGHSA enrichment
  52. 2026-09-09 01:36 UTCEG score recompute
  53. 2026-09-09 01:36 UTCGHSA enrichment
  54. 2026-09-08 22:01 UTCEPSS rescore
  55. 2026-09-07 19:41 UTCEG score recompute
  56. 2026-09-07 19:41 UTCGHSA enrichment
  57. 2026-09-07 16:01 UTCEPSS rescore
  58. 2026-09-06 17:35 UTCEG score recompute
  59. 2026-09-06 17:35 UTCGHSA enrichment
  60. 2026-09-06 13:47 UTCEPSS rescore
  61. 2026-09-05 15:28 UTCEG score recompute
  62. 2026-09-05 15:28 UTCGHSA enrichment
  63. 2026-09-04 13:20 UTCEG score recompute
  64. 2026-09-04 13:20 UTCGHSA enrichment
  65. 2026-09-04 05:07 UTCEPSS rescore
  66. 2026-09-03 11:11 UTCEG score recompute
  67. 2026-09-03 11:11 UTCGHSA enrichment
  68. 2026-09-02 14:12 UTCEPSS rescore
  69. 2026-09-02 09:02 UTCEG score recompute
  70. 2026-09-02 09:02 UTCGHSA enrichment
  71. 2026-09-01 13:54 UTCEPSS rescore
  72. 2026-09-01 06:52 UTCEG score recompute
  73. 2026-09-01 06:52 UTCGHSA enrichment
  74. 2026-09-01 04:40 UTCEPSS rescore
  75. 2026-08-31 04:45 UTCEG score recompute

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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 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 0.3% probability of exploitation in the next 30 days (16th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-5389?
CVE-2026-5389 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-2026-5389?
A fix for CVE-2026-5389 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-5389 are linked in the Vendor Advisories panel on this page.

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