CVE-2021-33391

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2023-02-17. NVD baseline CVSS 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Elevated
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 1%CVSS: 9.8Exploit: Elevated riskExposed: 0

A fix is available — apply it.

An issue in HTACG HTML Tidy v5.7.28 allows attacker to execute arbitrary code via the -g option of the CleanNode() function in gdoc.c.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
75(Attend)
EG Risk 75/100SSVC: Attend

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
Severity98% × 45%
Exploitation40% × 40%
Automatability100% × 15%
Action: Remediate soon — notable exploitation risk.
EPSS PROB
1%
EPSS %ILE
64%
KEV
Not listed

Published

February 17, 2023

Last Modified

March 18, 2025

Advisory Details (1)

Auto-updated Sep 3, 2026
No patch confirmed yet.
generic

Heap use-after-free in the CleanNode() function · Issue #946 · htacg/tidy-html5 · GitHub

https://github.com/htacg/tidy-html5/issues/946

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntutidy (2:5.6.0-11ubuntu0.23.10.1) @ mantic2026-05-25ubuntu

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(4 across 4 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
tidy-html52:5.6.0-11 ... 2:5.8.0-2.1 (7 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
tidy-html52:5.6.0-11 ... 2:5.8.0-2.1 (7 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
tidy-html5—2:5.8.0-2—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
tidy-html5—2:5.8.0-2—

Weakness Classification(1)

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

All Vendor Advisories

(2)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 9× in last 7d / 32× 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 152 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2021-33391?
CVE-2021-33391 is a critical vulnerability published on February 17, 2023. An issue in HTACG HTML Tidy v5.7.28 allows attacker to execute arbitrary code via the -g option of the CleanNode() function in gdoc.c.
When was CVE-2021-33391 disclosed?
CVE-2021-33391 was first published in the National Vulnerability Database on February 17, 2023, with the most recent update on March 18, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-33391 actively exploited?
CVE-2021-33391 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1% probability of exploitation in the next 30 days, which ranks it in the top 35.8% of all scored CVEs.
What is the CVSS score of CVE-2021-33391?
CVE-2021-33391 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2021-33391?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-33391, 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

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