# CVE-2026-49851

## Summary

- **CVE ID:** CVE-2026-49851
- **Severity:** HIGH
- **CVSS Score:** 8.7 (CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N)
- **CWE:** CWE-400, CWE-770, CWE-407
- **Published:** Jun 24, 2026
- **Last Modified:** Aug 28, 2026

## Description

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, Mistune is vulnerable to a CPU exhaustion DoS due to superlinear (approximately O(n²)) behavior in parse_link_text. When parsing Markdown containing many consecutive [ characters, parse_link_text repeatedly scans the input using a regex search inside a loop. Each iteration re-scans a large portion of the remaining string, resulting in quadratic-time behavior. An attacker-controlled Markdown input can therefore trigger excessive CPU usage with a very small payload. This vulnerability is fixed in 3.3.0.

## Affected Products

- lepture — mistune (< 3.3.0)

## References

- [CNA](https://github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96p)
- [redhat-SADP](https://access.redhat.com/security/cve/CVE-2026-49851)
- [redhat-SADP](https://bugzilla.redhat.com/show_bug.cgi?id=2492304)
- [redhat-SADP](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-49851.json)
- [redhat-SADP](https://access.redhat.com/errata/RHSA-2026:60520)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.63%
- **EPSS Percentile:** 48.1

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._