CVE-2026-49851
published 2026-06-24CVE-2026-49851: 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…
PriorityP340high7.5CVSS 3.1
AVNACLPRNUINSUCNINAH
EPSS
0.35%
27.1th percentile
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
24 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| lepture | mistune | < 3.3.0 | 3.3.0 |
| mistune_project | mistune | >= 0 < 3.3.0 | 3.3.0 |
| rhoai | odh-pipeline-runtime-datascience-cpu-py312-rhel9 | — | — |
| rhoai | odh-pipeline-runtime-minimal-cpu-py312-rhel9 | — | — |
| rhoai | odh-pipeline-runtime-pytorch-cuda-py312-rhel9 | — | — |
| rhoai | odh-pipeline-runtime-pytorch-llmcompressor-cuda-py312-rhel9 | — | — |
| rhoai | odh-pipeline-runtime-pytorch-rocm-py312-rhel9 | — | — |
| rhoai | odh-pipeline-runtime-tensorflow-cuda-py312-rhel9 | — | — |
| rhoai | odh-pipeline-runtime-tensorflow-rocm-py312-rhel9 | — | — |
| rhoai | odh-th06-cpu-torch210-py312-rhel9 | — | — |
| rhoai | odh-th06-cpu-torch291-py312-rhel9 | — | — |
| rhoai | odh-th06-cuda130-torch210-py312-rhel9 | — | — |
| rhoai | odh-th06-cuda130-torch291-py312-rhel9 | — | — |
| rhoai | odh-th06-rocm64-torch291-py312-rhel9 | — | — |
| rhoai | odh-workbench-jupyter-datascience-cpu-py312-rhel9 | — | — |
| rhoai | odh-workbench-jupyter-minimal-cpu-py312-rhel9 | — | — |
| rhoai | odh-workbench-jupyter-minimal-cuda-py312-rhel9 | — | — |
| rhoai | odh-workbench-jupyter-minimal-rocm-py312-rhel9 | — | — |
| rhoai | odh-workbench-jupyter-pytorch-cuda-py312-rhel9 | — | — |
| rhoai | odh-workbench-jupyter-pytorch-llmcompressor-cuda-py312-rhel9 | — | — |
| rhoai | odh-workbench-jupyter-pytorch-rocm-py312-rhel9 | — | — |
| rhoai | odh-workbench-jupyter-tensorflow-cuda-py312-rhel9 | — | — |
| rhoai | odh-workbench-jupyter-tensorflow-rocm-py312-rhel9 | — | — |
| rhoai | odh-workbench-jupyter-trustyai-cpu-py312-rhel9 | — | — |
CVSS provenance
nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
nvdv4.08.7HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
vendor_redhat8.7HIGH
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GHSA
Mistune: Potential DoS via quadratic-time parsing in parse_link_text
ghsa·2026-07-09
CVE-2026-49851 [HIGH] CWE-400 Mistune: Potential DoS via quadratic-time parsing in parse_link_text
Mistune: Potential DoS via quadratic-time parsing in parse_link_text
### Summary
Mistune is vulnerable to a CPU exhaustion DoS due to superlinear (approximately O(n²)) behavior in parse_link_text. A relatively small input consisting of repeated [ characters causes significant parsing slowdown.
### Affected component
mistune/inline_parser.py → **parse_link_text**
### Description
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.
### Root cause
The vulnerability stems from a two-loop interac
VulDB
lepture mistune up to 3.2.x Python Markdown Parser resource consumption (GHSA-qcq2-496w-v96p)
vuldb·2026-06-24·CVSS 8.7
CVE-2026-49851 [HIGH] lepture mistune up to 3.2.x Python Markdown Parser resource consumption (GHSA-qcq2-496w-v96p)
A vulnerability identified as problematic has been detected in lepture mistune up to 3.2.x. This issue affects some unknown processing of the component Python Markdown Parser. The manipulation leads to resource consumption.
This vulnerability is uniquely identified as CVE-2026-49851. The attack is possible to be carried out remotely. No exploit exists.
You should upgrade the affected component.
Red Hat
Mistune: Mistune: Denial of Service via crafted Markdown input
vendor_redhat·2026-06-24·CVSS 8.7
CVE-2026-49851 [HIGH] CWE-1333 Mistune: Mistune: Denial of Service via crafted Markdown input
Mistune: Mistune: Denial of Service via crafted Markdown input
A flaw was found in Mistune, a Python Markdown parser. A remote attacker can exploit this vulnerability by providing a specially crafted Markdown input containing many consecutive bracket characters. This can lead to excessive CPU usage, causing a denial-of-service (DoS) condition on the affected system.
Mitigation: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Package: mta/mta-solution-server-rhel9 (Migration Toolkit for Applications 8) - Not affected
Package: rhoai/odh-pipeline-runtime-datascience-cpu-py312-rhel9 (Red Hat OpenShift AI (
No detection rules found.
No public exploits indexed.
https://github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96phttps://access.redhat.com/security/cve/CVE-2026-49851https://bugzilla.redhat.com/show_bug.cgi?id=2492304https://github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96phttps://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-49851.json
2026-06-24
Published