CVE-2026-44899
published 2026-05-26CVE-2026-44899: Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, the Image directive plugin validates the :width: and :height: options with a…
PriorityP427medium6.1CVSS 3.1
AVNACLPRNUIRSCCLILAN
EPSS
0.23%
13.6th percentile
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, the Image directive plugin validates the :width: and :height: options with a regex compiled as _num_re = re.compile(r"^\d+(?:\.\d*)?"). When the validated value is not a plain integer, render_block_image() inserts it directly into a style="width:...;" or style="height:...;" attribute. Because the value was accepted by the prefix-only regex, any CSS after the leading digits reaches the style= attribute verbatim and without escaping. This vulnerability is fixed in 3.2.1.
Affected
26 ranges· showing 25
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| lepture | mistune | < 3.2.1 | 3.2.1 |
| mistune_project | mistune | < 3.2.1 | 3.2.1 |
| mistune_project | mistune | >= 3.2.0 < 3.2.1 | 3.2.1 |
| mta | mta-solution-server-rhel9 | — | — |
| 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 | — | — |
CVSS provenance
nvdv3.16.1MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
vendor_redhat6.1MEDIUM
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VulDB
lepture mistune up to 3.2.0 Python Markdown Parser render_block_image cross site scripting (GHSA-ccfx-mfmx-2fx9)
vuldb·2026-05-26·CVSS 4.7
CVE-2026-44899 [MEDIUM] lepture mistune up to 3.2.0 Python Markdown Parser render_block_image cross site scripting (GHSA-ccfx-mfmx-2fx9)
A vulnerability was found in lepture mistune up to 3.2.0. It has been classified as problematic. The affected element is the function render_block_image of the component Python Markdown Parser. Performing a manipulation results in cross site scripting.
This vulnerability is identified as CVE-2026-44899. The attack can be initiated remotely. There is not any exploit available.
Upgrading the affected component is recommended.
GHSA
Mistune Image Directive CSS Injection Vulnerability
ghsa·2026-05-14
CVE-2026-44899 [MEDIUM] CWE-79 Mistune Image Directive CSS Injection Vulnerability
Mistune Image Directive CSS Injection Vulnerability
## Summary
The Image directive plugin validates the `:width:` and `:height:` options with a regex compiled as `_num_re = re.compile(r"^\d+(?:\.\d*)?")`. This pattern is applied via `re.match()` (which anchors only at the **start** of the string, not the end). Any value that begins with one or more digits passes validation, regardless of what follows.
When the validated value is not a plain integer, `render_block_image()` inserts it directly into a `style="width:...;"` or `style="height:...;"` attribute. Because the value was accepted by the prefix-only regex, any CSS after the leading digits reaches the `style=` attribute verbatim and without escaping.
An attacker can therefore inject an arbitrary chain of CSS properties — including `p
Red Hat
python-mistune: Mistune: Information disclosure via CSS injection in Image directive plugin
vendor_redhat·2026-05-26·CVSS 6.1
CVE-2026-44899 [MEDIUM] CWE-1286 python-mistune: Mistune: Information disclosure via CSS injection in Image directive plugin
python-mistune: Mistune: Information disclosure via CSS injection in Image directive plugin
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, the Image directive plugin validates the :width: and :height: options with a regex compiled as _num_re = re.compile(r"^\d+(?:\.\d*)?"). When the validated value is not a plain integer, render_block_image() inserts it directly into a style="width:...;" or style="height:...;" attribute. Because the value was accepted by the prefix-only regex, any CSS after the leading digits reaches the style= attribute verbatim and without escaping. This vulnerability is fixed in 3.2.1.
A flaw was found in Mistune, a Python Markdown parser. The Image directive plugin, responsible for handling image dimensions, improperly validates user-
No detection rules found.
No public exploits indexed.
2026-05-26
Published