CVE-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 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.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96p
https://access.redhat.com/security/cve/CVE-2026-49851
https://bugzilla.redhat.com/show_bug.cgi?id=2492304
https://github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96p
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-49851.json

Configurations

No configuration.

History

30 Jun 2026, 03:20

Type	Values Removed	Values Added
CVSS	v2 : ~~unknown~~ v3 : ~~unknown~~	v2 : unknown v3 : 7.5
CWE		CWE-1333
References		() https://access.redhat.com/security/cve/CVE-2026-49851 - () https://bugzilla.redhat.com/show_bug.cgi?id=2492304 - () https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-49851.json -

25 Jun 2026, 20:18

Type	Values Removed	Values Added
References	~~() https://github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96p -~~	() https://github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96p -

24 Jun 2026, 18:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-06-24 18:17

Updated : 2026-07-15 02:22

NVD link : CVE-2026-49851

Mitre link : CVE-2026-49851

CVE.ORG link : CVE-2026-49851

JSON object : View

Products Affected

No product.

CWE

CWE-400

Uncontrolled Resource Consumption

CWE-407

Inefficient Algorithmic Complexity

CWE-770

Allocation of Resources Without Limits or Throttling

CWE-1333

Inefficient Regular Expression Complexity

{"id": "CVE-2026-49851", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"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"}}], "cvssMetricV31": [{"type": "Secondary", "source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 7.5, "attackVector": "NETWORK", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}, "impactScore": 3.6, "exploitabilityScore": 3.9}], "cvssMetricV40": [{"type": "Secondary", "source": "security-advisories@github.com", "cvssData": {"Safety": "NOT_DEFINED", "version": "4.0", "Recovery": "NOT_DEFINED", "baseScore": 8.7, "Automatable": "NOT_DEFINED", "attackVector": "NETWORK", "baseSeverity": "HIGH", "valueDensity": "NOT_DEFINED", "vectorString": "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/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", "exploitMaturity": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "userInteraction": "NONE", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "subIntegrityImpact": "NONE", "vulnIntegrityImpact": "NONE", "integrityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "vulnAvailabilityImpact": "HIGH", "availabilityRequirement": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "subConfidentialityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "confidentialityRequirement": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED"}}]}, "affected": [{"source": "security-advisories@github.com", "affectedData": [{"vendor": "lepture", "product": "mistune", "versions": [{"status": "affected", "version": "< 3.3.0"}]}]}, {"source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "affectedData": [{"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"}]}], "published": "2026-06-24T18:17:18.937", "references": [{"url": "https://github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96p", "source": "security-advisories@github.com"}, {"url": "https://access.redhat.com/security/cve/CVE-2026-49851", "source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c"}, {"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2492304", "source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c"}, {"url": "https://github.com/lepture/mistune/security/advisories/GHSA-qcq2-496w-v96p", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"}, {"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-49851.json", "source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c"}], "vulnStatus": "Deferred", "weaknesses": [{"type": "Secondary", "source": "security-advisories@github.com", "description": [{"lang": "en", "value": "CWE-400"}, {"lang": "en", "value": "CWE-407"}, {"lang": "en", "value": "CWE-770"}]}, {"type": "Secondary", "source": "0b0ca135-0b70-47e7-9f44-1890c2a1c46c", "description": [{"lang": "en", "value": "CWE-1333"}]}], "descriptions": [{"lang": "en", "value": "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(n\u00b2)) 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."}], "lastModified": "2026-07-15T02:22:36.243", "sourceIdentifier": "security-advisories@github.com"}