8.7
HIGH
CVSS 4.0
CVE-2026-49851
Mistune: Potential DoS via quadratic-time parsing in parse_link_text
Overview
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.
Details
INFO
Published Date :
June 24, 2026, 6:17 p.m.
Last Modified :
July 15, 2026, 2:22 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Scoring
CVSS Scores
The Common Vulnerability Scoring System is a standardized framework
for assessing the severity of vulnerabilities in software and systems.
We collect and displays CVSS scores from various sources for each CVE.
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | ||||
| CVSS 4.0 | HIGH | [email protected] |
Solution
Update Mistune to version 3.3.0 or later to fix CPU exhaustion DoS.
- Update Mistune to version 3.3.0 or later.
- Avoid parsing untrusted Markdown input.
References
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-49851.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-49851 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-49851
weaknesses.
CAPEC-147: XML Ping of the Death XML Ping of the Death
CAPEC-227: Sustained Client Engagement Sustained Client Engagement
CAPEC-492: Regular Expression Exponential Blowup Regular Expression Exponential Blowup
CAPEC-125: Flooding Flooding
CAPEC-130: Excessive Allocation Excessive Allocation
CAPEC-147: XML Ping of the Death XML Ping of the Death
CAPEC-197: Exponential Data Expansion Exponential Data Expansion
CAPEC-229: Serialized Data Parameter Blowup Serialized Data Parameter Blowup
CAPEC-230: Serialized Data with Nested Payloads Serialized Data with Nested Payloads
CAPEC-231: Oversized Serialized Data Payloads Oversized Serialized Data Payloads
CAPEC-469: HTTP DoS HTTP DoS
CAPEC-482: TCP Flood TCP Flood
CAPEC-486: UDP Flood UDP Flood
CAPEC-487: ICMP Flood ICMP Flood
CAPEC-488: HTTP Flood HTTP Flood
CAPEC-489: SSL Flood SSL Flood
CAPEC-490: Amplification Amplification
CAPEC-491: Quadratic Data Expansion Quadratic Data Expansion
CAPEC-493: SOAP Array Blowup SOAP Array Blowup
CAPEC-494: TCP Fragmentation TCP Fragmentation
CAPEC-495: UDP Fragmentation UDP Fragmentation
CAPEC-496: ICMP Fragmentation ICMP Fragmentation
CAPEC-528: XML Flood XML Flood
CAPEC-492: Regular Expression Exponential Blowup Regular Expression Exponential Blowup
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-49851 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-49851 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Modified by 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Jul. 15, 2026
Action Type Old Value New Value Changed Affected [{'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:migration_toolkit_applications:8'], 'vendor': 'Red Hat', 'product': 'Migration Toolkit for Applications 8', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/a:redhat:openshift:4'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift Container Platform 4', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/a:redhat:satellite:6'], 'vendor': 'Red Hat', 'product': 'Red Hat Satellite 6', 'defaultStatus': 'unaffected'}] [{'cpes': ['cpe:/a:redhat:migration_toolkit_applications:8'], 'vendor': 'Red Hat', 'product': 'Migration Toolkit for Applications 8', 'packageName': 'mta/mta-solution-server-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-pipeline-runtime-datascience-cpu-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-pipeline-runtime-minimal-cpu-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-pipeline-runtime-pytorch-cuda-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-pipeline-runtime-pytorch-llmcompressor-cuda-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-pipeline-runtime-pytorch-rocm-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-pipeline-runtime-tensorflow-cuda-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-pipeline-runtime-tensorflow-rocm-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-th06-cpu-torch210-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-th06-cpu-torch291-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-th06-cuda130-torch210-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-th06-cuda130-torch291-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-th06-rocm64-torch291-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-workbench-jupyter-datascience-cpu-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-workbench-jupyter-minimal-cpu-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-workbench-jupyter-minimal-cuda-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-workbench-jupyter-minimal-rocm-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-workbench-jupyter-pytorch-cuda-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-workbench-jupyter-pytorch-llmcompressor-cuda-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-workbench-jupyter-pytorch-rocm-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-workbench-jupyter-tensorflow-cuda-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-workbench-jupyter-tensorflow-rocm-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'packageName': 'rhoai/odh-workbench-jupyter-trustyai-cpu-py312-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:openshift:4'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift Container Platform 4', 'packageName': 'python-mistune', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/a:redhat:satellite:6'], 'vendor': 'Red Hat', 'product': 'Red Hat Satellite 6', 'packageName': 'satellite/iop-advisor-engine-rhel9', 'collectionURL': 'https://access.redhat.com/downloads/content/package-browser/', 'defaultStatus': 'unaffected'}] -
CVE Modified by 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Jun. 30, 2026
Action Type Old Value New Value Added Affected [{'cpes': ['cpe:/a:redhat:openshift_ai'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift AI (RHOAI)', 'defaultStatus': 'affected'}, {'cpes': ['cpe:/a:redhat:migration_toolkit_applications:8'], 'vendor': 'Red Hat', 'product': 'Migration Toolkit for Applications 8', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/a:redhat:openshift:4'], 'vendor': 'Red Hat', 'product': 'Red Hat OpenShift Container Platform 4', 'defaultStatus': 'unaffected'}, {'cpes': ['cpe:/a:redhat:satellite:6'], 'vendor': 'Red Hat', 'product': 'Red Hat Satellite 6', 'defaultStatus': 'unaffected'}] Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-1333 Added Reference https://access.redhat.com/security/cve/CVE-2026-49851 Added Reference https://bugzilla.redhat.com/show_bug.cgi?id=2492304 Added Reference https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-49851.json -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jun. 25, 2026
Action Type Old Value New Value Added Reference https://github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96p Added SSVC {'id': 'CVE-2026-49851', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-06-25T19:55:32.245725Z'} -
New CVE Received by [email protected]
Jun. 24, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'lepture', 'product': 'mistune', 'versions': [{'status': 'affected', 'version': '< 3.3.0'}]}] Added 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. Added CVSS V4.0 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 Added CWE CWE-407 Added CWE CWE-400 Added CWE CWE-770 Added Reference https://github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96p
EPSS is a daily estimate of the probability of exploitation activity
being observed over the next 30 days. Following chart shows the EPSS
score history of the vulnerability.