CVE-2026-59928

HIGHPre-NVD 7.57.5—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 71% 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, secondary
Trending — 3 sources updated this weekElevated
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.5Exploit: 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 3.3.0, a Markdown document containing many repeated or distinct reference-link definitions causes quadratic work in src/mistune/block_parser.py and the ref_links environment dictionary handling, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.

CVSS v3
7.5
EG Score
7.5(medium)
EPSS
28.7%
KEV
Not listed

Published

July 8, 2026

Last Modified

July 9, 2026

Advisory Details (3)

Auto-updated Jul 8, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github_release, github.
github Patch Available🟡 PoC Available

block_parser: quadratic-time parsing on long lists of repeated reference-link definitions · Advisory · lepture/mistune · GitHub

https://github.com/lepture/mistune/security/advisories/GHSA-ffq3-xpv3-j92q
github_release Patch Available

v3.3.0

Patch available: lepture/mistune v3.3.0

https://github.com/lepture/mistune/releases/tag/v3.3.0
github_commit Patch Available

commit 2b04d7ba341c (lepture/mistune)

Patch available: lepture/mistune v3.3.0 (contains commit 2b04d7ba341c)

https://github.com/lepture/mistune/commit/2b04d7ba341c16ac78fe82d3076bdd5c3de87c69

Vendor Advisories for CVE-2026-59928(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 13× in last 7d / 13× 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. 2026-07-12 01:09 UTCEG score recompute
  2. 2026-07-11 13:42 UTCEG score recompute
  3. 2026-07-11 08:27 UTCEPSS rescore
  4. 2026-07-11 08:27 UTCEPSS rescore
  5. 2026-07-11 02:15 UTCEG score recompute
  6. 2026-07-10 14:46 UTCEG score recompute
  7. 2026-07-10 03:19 UTCEG score recompute
  8. 2026-07-09 19:10 UTCEPSS rescore
  9. 2026-07-09 19:10 UTCEPSS rescore
  10. 2026-07-09 15:51 UTCEG score recompute
  11. 2026-07-09 04:23 UTCEG score recompute
  12. 2026-07-08 16:56 UTCEG score recompute
  13. 2026-07-08 16:55 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-59928?
CVE-2026-59928 is a high vulnerability published on July 8, 2026. Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a Markdown document containing many repeated or distinct reference-link definitions causes quadratic work in src/mistune/blockparser.py and the reflinks environment dictionary handling, allowing denial of service…
When was CVE-2026-59928 disclosed?
CVE-2026-59928 was first published in the National Vulnerability Database on July 8, 2026, with the most recent update on July 9, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-59928 actively exploited?
CVE-2026-59928 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 28.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-59928?
CVE-2026-59928 has a CVSS v3 base score of 7.5 (NVD).
How do I remediate CVE-2026-59928?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-59928, 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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