How severe is CVE-2026-59928?

CVE-2026-59928 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-59928 being actively exploited?

It is not currently listed in CISA's Known Exploited Vulnerabilities catalog, and no EPSS exploit-prediction score is available yet.

How do I fix CVE-2026-59928?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2026-59928 published?

CVE-2026-59928 was published on 2026-07-08.

CVE-2026-59928

CVE-2026-59928 is a high-severity vulnerability with a CVSS 3.x base score of 7.5. The underlying weakness is classified as CWE-407.

Key facts

Severity: High (CVSS 3.x base score 7.5)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-407
Published: 2026-07-08
Last modified: 2026-07-08

Description

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.

Frequently asked questions

What is CVE-2026-59928?: 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.
How severe is CVE-2026-59928?: CVE-2026-59928 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-59928 being actively exploited?: It is not currently listed in CISA's Known Exploited Vulnerabilities catalog, and no EPSS exploit-prediction score is available yet.
How do I fix CVE-2026-59928?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-59928 published?: CVE-2026-59928 was published on 2026-07-08.

References

Other CWE-407 vulnerabilities

CVE-2026-57480 — High (CVSS 8.7): Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to…
CVE-2026-55206 — High (CVSS 8.7): py7zr is a Python-based library and utility to support 7zip archive compression, decompression, encryption and…
CVE-2026-59880 — High (CVSS 8.7): Immutable.js provides many Persistent Immutable data structures. Prior to 4.3.9 and 5.1.8, Immutable.Map and…
CVE-2026-58226 — High (CVSS 8.7): Inefficient Algorithmic Complexity vulnerability in elixir-mint hpax allows unauthenticated denial-of-service via…
CVE-2026-54892 — High (CVSS 8.7): Inefficient algorithmic complexity in Plug's nested-parameter decoder allows an unauthenticated remote attacker to…
CVE-2026-56669 — High (CVSS 7.5): Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation, and client-server…

Browse all CWE-407 vulnerabilities →