CVE-2026-77088

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 — 4 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%CVSS: 6.1Exploit: None knownExposed: 0

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

justhtml versions 0.9.0 through 1.21.0 contain a cross-site scripting vulnerability in to_markdown() where inline code spans fail to account for blank lines as block boundaries. Attackers can inject blank lines into code or pre element text to break the inline span, causing sanitized HTML to be emitted unescaped and re-parsed as live Markdown by compliant 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%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
8%
KEV
Not listed

Published

August 23, 2026

Last Modified

August 29, 2026

Advisory Details (2)

Auto-updated Aug 23, 2026
🔬 Proof of concept available. Patch available. Sources: github.
generic

justhtml 0.9.0 through 1.21.0 Cross-Site Scripting via code-span | Advisories | VulnCheck

https://www.vulncheck.com/advisories/justhtml-through-cross-site-scripting-via-code-span
github Patch Available🟡 PoC Available

justhtml: to_markdown() code-span blank-line breakout enables XSS · Advisory · EmilStenstrom/justhtml · GitHub

https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-jf6w-2mvx-633j

Vendor Advisories for CVE-2026-77088(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
justhtml0.10.0 ... 1.9.1 (56 versions)1.22.0—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 25× in last 7d / 25× 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. 2026-08-30 01:22 UTCEPSS rescore
  2. 2026-08-29 12:23 UTCEG score recompute
  3. 2026-08-29 12:23 UTCGHSA enrichment
  4. 2026-08-29 12:04 UTCEG score recompute
  5. 2026-08-29 12:03 UTCGHSA enrichment
  6. 2026-08-29 00:32 UTCEG score recompute
  7. 2026-08-29 00:31 UTCGHSA enrichment
  8. 2026-08-28 21:42 UTCEPSS rescore
  9. 2026-08-27 19:48 UTCEG score recompute
  10. 2026-08-27 19:48 UTCGHSA enrichment
  11. 2026-08-27 14:25 UTCEPSS rescore
  12. 2026-08-26 17:24 UTCEG score recompute
  13. 2026-08-26 17:24 UTCGHSA enrichment
  14. 2026-08-26 16:23 UTCEG score recompute
  15. 2026-08-26 16:23 UTCGHSA enrichment
  16. 2026-08-26 14:47 UTCEPSS rescore
  17. 2026-08-25 19:22 UTCEG score recompute
  18. 2026-08-25 19:22 UTCGHSA enrichment
  19. 2026-08-25 13:49 UTCEPSS rescore
  20. 2026-08-24 16:55 UTCEG score recompute
  21. 2026-08-24 16:55 UTCGHSA enrichment
  22. 2026-08-24 14:18 UTCEPSS rescore
  23. 2026-08-23 14:20 UTCEG score recompute
  24. 2026-08-23 13:51 UTCEG score recompute
  25. 2026-08-23 13:50 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-77088?
CVE-2026-77088 is a medium vulnerability published on August 23, 2026. justhtml versions 0.9.0 through 1.21.0 contain a cross-site scripting vulnerability in to_markdown() where inline code spans fail to account for blank lines as block boundaries. Attackers can inject blank lines into code or pre element text to break the inline span, causing sanitized HTML to be…
When was CVE-2026-77088 disclosed?
CVE-2026-77088 was first published in the National Vulnerability Database on August 23, 2026, with the most recent update on August 29, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-77088 actively exploited?
CVE-2026-77088 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 91.5% of all scored CVEs.
What is the CVSS score of CVE-2026-77088?
CVE-2026-77088 has a CVSS v3 base score of 6.1 (NVD).
How do I remediate CVE-2026-77088?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-77088, 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-2026-77088

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