CVE-2026-44896: Mistune: XSS via unescaped figclass/figwidth in Figure directive
Vulnerability summary
CVE-2026-44896 is a medium (CVSS 6.1) vulnerability in lepture mistune. EPSS estimates a 0.20% chance of exploitation in the next 30 days, higher than 9.6% of scored vulnerabilities.
Not severe (CVSS 5.3, network access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 2 · Related 3Timeline
- 26-05-2026PublishedVulnerability first disclosed.
- 08-06-2026Last modifiedVulnerability information updated.
Description
Mistune is a Python Markdown parser with renderers and plugins. In 3.2.0 and earlier, in src/mistune/directives/image.py, the render_figure() function concatenates figclass and figwidth options directly into HTML attributes without escaping. This allows attribute injection and XSS even when HTMLRenderer(escape=True) is used, because these values bypass the inline renderer. Version 3.2.1 contains a patch.
CVSS metrics
9 scores · 7 sources · 2 versions- OSV · UbuntuEcosystem advisory · calculated5.3MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
- OSV · WolfiEcosystem advisory · calculated5.3MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
- OSV · ChainguardEcosystem advisory · calculated5.3MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
- NVDNIST5.3MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/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
- OSV · PypiEcosystem advisory · calculated6.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- OSV · UbuntuEcosystem advisory · calculated6.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- OSV · DebianEcosystem advisory · calculated6.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
EPSS trend
Probability
0.20%
Chance of exploitation in the next 30 days
Percentile
10%
Versus all other CVEs
30-day change
Decrease -0.07 pp
From 0.27% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, user interaction (CVSS vector). Other conditions: not stated in public data.
Chainguard2 products
- datahub-ingestion-fips< 1.5.0.1-r2
- kubeflow-pipelines-visualization-server< 2.16.1-r2
Ubuntu2 products
- mistuneAll versions (No fix recorded)
- mistune0All versions (No fix recorded)
Debian1 product
- mistuneAll versions (No fix recorded)
Lepture1 product
- mistune< 3.2.1
Mistune_project1 product
- mistune≤ 3.2.0
PyPI1 product
- mistune< 3.2.1
Wolfi1 product
- kubeflow-pipelines-visualization-server< 2.16.1-r2
7 vendors · 9 products
References
9 links- github.com/lepture/mistune/security/advisories/GHSA-58cw-g322-p94vX Refsource CONFIRMWEBAdvisoryREPORTVendor Advisory
- github.com/lepture/mistunePACKAGE
