Is CVE-2026-115349 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-115349 being exploited in the wild.

How severe is CVE-2026-115349?

High severity, with a CVSS score of 7.5, published 22 October 2026.

Which products and versions are affected?

Lepture Mistune 3.0.0 to 3.2.1.

Is there a fix for CVE-2026-115349?

Yes: fixed in 3.3.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-115349 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-115349?

Check whether you run Lepture Mistune at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-115349: Mistune ReDoS in parse_link_text function

CVE-2026-115349 · Severity: high · CVSS 7.5 · Published 2026-10-22

Mistune is a markdown parser library used by web applications and content management systems to convert user-supplied markdown text into HTML. A denial-of-service vulnerability allows attackers to exhaust server CPU by submitting markdown with deeply nested square brackets, causing parsing times to grow quadratically with input size. A small request with roughly 16KB of crafted markdown can consume over 70 seconds of CPU time, and multiple concurrent requests can completely disable a server.

Technologies: Lepture Mistune. Vendors: Lepture.

Quick answers

Is CVE-2026-115349 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-115349 being exploited in the wild.
How severe is CVE-2026-115349?: High severity, with a CVSS score of 7.5, published 22 October 2026.
Which products and versions are affected?: Lepture Mistune 3.0.0 to 3.2.1.
Is there a fix for CVE-2026-115349?: Yes: fixed in 3.3.0. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-115349 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-115349?: Check whether you run Lepture Mistune at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

Fixed in: 3.3.0

Technical details

The parse_link_text function in src/mistune/helpers.py uses a regex search loop that scans through all remaining brackets for each opening bracket encountered, resulting in O(n²) complexity when processing input with n nested brackets. The function lacks depth limits or input length checks. An unauthenticated network attacker can trigger this via any markdown parsing endpoint without user interaction, causing severe availability impact through CPU exhaustion.

Affected products

Lepture Mistune 3.0.0 to 3.2.1

Timeline

2026-06-21: disclosed: GitHub Security Advisory GHSA-3q64-rw38-243v published
2026-10-22: advisory: CVE-2026-115349 published on NVD

References

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