How severe is CVE-2026-46637?

No CVSS score has been assigned to CVE-2026-46637 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-46637?

CVE-2026-46637 affects the following packages: twig/markdown-extra (Packagist), twig/cssinliner-extra (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2026-46637?

Update twig/markdown-extra to 3.26.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-46637 is resolved across your whole dependency graph.

How do I detect CVE-2026-46637 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for twig/markdown-extra, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-46637 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2026-46637 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-46637 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-46637?

CVE-2026-46637 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 21th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-46637?

CVE-2026-46637 is classified as CWE-116 (CWE-116), Cross-site Scripting (XSS) (CWE-79). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-46637 published, and has it been updated?

CVE-2026-46637 was published on July 14, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘 Packagist

Not in CISA KEV

CVE-2026-46637 — twig/markdown-extra

Fix: twigphp/Twig@8498207

CVE-2026-46637 is a CWE-116 vulnerability in twig/markdown-extra. A fix is available for twig/markdown-extra — see the affected versions and patch details below.

Twig: HTML-output filters in twig/* extras incorrectly declared `is_safe => ['all']`

Also known asGHSA-jv8m-2544-3pg3

Published

Jul 14, 2026

Updated

Aug 12, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 2, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-46637.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs21th percentile — riskier than 21% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

2 pkgs affected

🐘twig/markdown-extra🐘twig/cssinliner-extra

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Several filters in the twig/* extras packages are registered with is_safe => ['all'], which tells Twig's autoescaper to treat their output as safe in every context (html, js, css, url, ...). The output of these filters is plain text or HTML markup, neither of which is safe in every escaping context.

Affected filters:

html_to_markdown (twig/markdown-extra) emits plain Markdown text. league/html-to-markdown decodes HTML entities when producing code spans and fenced blocks, so an attacker-controlled <code><img src=x onerror=alert(1)></code> becomes `<img src=x onerror=alert(1)>`, which renders live when interpolated into an HTML page.
markdown_to_html (twig/markdown-extra) emits HTML. Safe in an HTML context but not in JS, CSS or URL contexts (e.g. when interpolated into an inline <script> block).
inline_css (twig/cssinliner-extra) emits HTML with inlined styles. Same constraint as markdown_to_html.

In all three cases, is_safe => ['all'] causes the autoescaper to emit the output verbatim in any context, even when the developer never wrote |raw. In a context such as a JS string or a URL parameter, this produces unescaped HTML and is exploitable as XSS.

Resolution

html_to_markdown no longer claims to be safe in any escaping context; its plain-text output is now autoescaped for the surrounding context.
markdown_to_html and inline_css are now declared is_safe => ['html'], asserting only what they actually guarantee.

Credits

Twig would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix for html_to_markdown and markdown_to_html in twig/markdown-extra, and Christophe Coevoet for extending the audit to inline_css in twig/cssinliner-extra.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`twig/markdown-extra`	all versions	3.26.0`composer require twig/markdown-extra:^3.26.0`
🐘Packagist	`twig/cssinliner-extra`	all versions	3.26.0`composer require twig/cssinliner-extra:^3.26.0`

Affected Products

1 product · 1 configurations

Application

twigsymfony

< 3.26.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for twig/markdown-extra, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update twig/markdown-extra to 3.26.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-46637 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

### Description Several filters in the `twig/*` extras packages are registered with `is_safe => ['all']`, which tells Twig's autoescaper to treat their output as safe in every context (`html`, `js`, `css`, `url`, ...). The output of these filters is plain text or HTML markup, neither of which is safe in every escaping context. Affected filters: - `html_to_markdown` (`twig/markdown-extra`) emits plain Markdown text. `league/html-to-markdown` decodes HTML entities when producing code spans and fenced blocks, so an attacker-controlled `<code><img src=x onerror=alert(1)></code>` becomes `

O3 Security · Impact-Aware SCA

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CVE-2026-46637 — twig/markdown-extra

Exploitation Status

No confirmed exploitation observed yet

EPSS Exploitation Probability

Real-World Exposure

Description

Description

Resolution

Credits

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is CVE-2026-46637 in your dependencies?