CVE-2026-44899

MEDIUMNVD 4.74.7—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 4.7 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 87% 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, nvd
Elevated
4.7
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 4.7Exploit: NoneExposed: 0

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

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, the Image directive plugin validates the :width: and :height: options with a regex compiled as _num_re = re.compile(r"^\d+(?:\.\d*)?"). When the validated value is not a plain integer, render_block_image() inserts it directly into a style="width:...;" or style="height:...;" attribute. Because the value was accepted by the prefix-only regex, any CSS after the leading digits reaches the style= attribute verbatim and without escaping. This vulnerability is fixed in 3.2.1.

CVSS v3
4.7
EG Score
4.7(medium)
EPSS
13.5%
KEV
Not listed

Published

May 14, 2026

Last Modified

May 28, 2026

Advisory Details (2)

Auto-updated Jun 17, 2026
🔬 Proof of concept available. Patch available. Sources: github_release, github.
github Patch Available🟡 PoC Available

Mistune Image Directive CSS Injection Vulnerability · Advisory · lepture/mistune · GitHub

https://github.com/lepture/mistune/security/advisories/GHSA-ccfx-mfmx-2fx9
github_release Patch Available

v3.2.1

Patch available: lepture/mistune v3.2.1

https://github.com/lepture/mistune/releases/tag/v3.2.1

Vendor Advisories for CVE-2026-44899(2)

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
mistune3.2.03.2.1—

Weakness Classification(1)

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

Data Freshness Timeline

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

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-44899?
CVE-2026-44899 is a medium vulnerability published on May 14, 2026. Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, the Image directive plugin validates the :width: and :height: options with a regex compiled as numre = re.compile(r"^\d+(?:\.\d*)?"). When the validated value is not a plain integer, renderblockimage() inserts it…
When was CVE-2026-44899 disclosed?
CVE-2026-44899 was first published in the National Vulnerability Database on May 14, 2026, with the most recent update on May 28, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-44899 actively exploited?
CVE-2026-44899 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 13.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-44899?
CVE-2026-44899 has a CVSS v3 base score of 4.7 (NVD).
How do I remediate CVE-2026-44899?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-44899, 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-2026-44899

Explore →

Is Your Infrastructure Affected by CVE-2026-44899?

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

Start Free Scan →Browse All CVEs