EUVD-2026-42335Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Unauthenticated remote input to a default parser (AV:N/AC:L/PR:N/UI:N) with a trivially crafted payload; impact is CPU-exhaustion DoS only, so C:N/I:N/A:H.
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
2DescriptionCVE.org
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, long sequences of well-formed double-asterisk or triple-asterisk emphasis pairs around a character cause quadratic work in src/mistune/inline_parser.py because the parser scans forward for matching close markers from every potential opening run, allowing denial of service in default Mistune parsing. This issue is fixed in version 3.3.0.
Articles & Coverage 1
AnalysisAI
Denial of service in Mistune, a widely used pure-Python Markdown parser, affects all versions prior to 3.3.0 where the default inline parser exhibits quadratic (O(n²)) behavior on long runs of well-formed double- or triple-asterisk emphasis pairs. Because the parser rescans forward for matching close markers from every candidate opening run, a small crafted Markdown payload forces disproportionate CPU consumption, exhausting resources on any service that renders untrusted Markdown. …
Unlock full vulnerability intelligence
- Risk assessment & exploitation conditions
- Attack chain visualization
- Remediation with exact patch versions
- Threat intelligence from 22 sources
- Personal watchlist & email alerts
Free forever · No credit card required
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires only that the target application pass attacker-controlled text through Mistune's default inline parser - the vulnerable emphasis handling is active in default Mistune parsing, so no special plugin, renderer, or non-default option must be enabled. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H, base 7.5) cleanly matches the described flaw: network-reachable, no authentication, no user interaction, and impact confined to availability with no confidentiality or integrity effect. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker submits a comment, chat message, or API request containing a crafted Markdown string with a long sequence of `**`/`***` emphasis pairs to any endpoint that renders Markdown with a vulnerable Mistune version. The server's parser enters quadratic processing, consuming excessive CPU on a single unauthenticated request (AV:N/AC:L/PR:N/UI:N); repeating the request across connections can exhaust worker threads and take the service offline. … |
| Remediation | Vendor-released patch: upgrade to Mistune 3.3.0 (https://github.com/lepture/mistune/releases/tag/v3.3.0), which rewrites the emphasis-scanning logic per commit 5de41fb8e527004dbc363e047a3c380c9288c74f; review the advisory at https://github.com/lepture/mistune/security/advisories/GHSA-4j32-57v6-6g45 for details. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Identify all services using Mistune and determine whether they process untrusted Markdown (user comments, submissions, API input). …
Sign in for detailed remediation steps and compensating controls.
Threat intelligence, references, and detailed analysis are available after sign-in.
Wazuh SIEM platform versions 4.4.0 through 4.9.0 contain an unsafe deserialization vulnerability in the DistributedAPI t
BentoML version 1.4.2 and earlier contains an unauthenticated remote code execution vulnerability through insecure deser
pgAdmin 4 contains critical remote code execution vulnerabilities in the Query Tool download and Cloud Deployment endpoi
The renderLocalView function in render/views.py in graphite-web in Graphite 0.9.5 through 0.9.10 uses the pickle Python
BentoML is a Python library for building online serving systems optimized for AI apps and model inference. Rated critica
OpenSSL before 0.9.8za, 1.0.0 before 1.0.0m, and 1.0.1 before 1.0.1h does not properly restrict processing of ChangeCiph
pyLoad download manager version prior to 0.5.0b3.dev77 exposes the Flask SECRET_KEY through an unauthenticated endpoint.
In Mercurial before 4.1.3, "hg serve --stdio" allows remote authenticated users to launch the Python debugger, and conse
Unauthenticated remote code execution in Marimo ≤0.20.4 allows attackers to execute arbitrary system commands via the `/
pyLoad is the free and open-source Download Manager written in pure Python. Rated medium severity (CVSS 5.3), this vulne
Langflow (a visual LLM pipeline builder) contains a critical unauthenticated code execution vulnerability (CVE-2026-3301
Cross-user flow execution in Langflow (< 1.9.1) lets any authenticated API-key holder run another user's flow by passing
Same weakness CWE-407 – Inefficient Algorithmic Complexity
View allSame technique Denial Of Service
View allShare
External POC / Exploit Code
Leaving vuln.today