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CVE-2026-46637

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

5.1 MediumFix available

Twig is a template language for PHP. Prior to 3.26.0, several filters in twig/markdown-extra and twig/cssinliner-extra are registered with is_safe => [all], causing Twig to treat plain text or HTML output as safe in HTML, JavaScript, CSS, URL, and other contexts where the output is not properly escaped. This issue is fixed in version 3.26.0.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
Passive

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
None

Exploit likelihood

0.30%Up 0.2 points since Jun 12, 2026
90%50%10%1%

What each source reports

CVE List Score used 5.1

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

Twig is a template language for PHP. Prior to 3.26.0, several filters in twig/markdown-extra and twig/cssinliner-extra are registered with is_safe => [all], causing Twig to treat plain text or HTML output as safe in HTML, JavaScript, CSS, URL, and other contexts where the output is not properly escaped. This issue is fixed in version 3.26.0.

Record
CVE-2026-46637
CVSS 4.0
5.1 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Weakness
CWE-116
Updated
2026-11-02
EUVDEUVD-2026-44509 5.1

Twig is a template language for PHP. Prior to 3.26.0, several filters in twig/markdown-extra and twig/cssinliner-extra are registered with is_safe => [all], causing Twig to treat plain text or HTML output as safe in HTML, JavaScript, CSS, URL, and other contexts where the output is not properly escaped. This issue is fixed in version 3.26.0.

Record
EUVD-2026-44509
CVSS 4.0
5.1 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-jv8m-2544-3pg3 1.3

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

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>&lt;img src=x onerror=alert(1)&gt;</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.

Record
GHSA-jv8m-2544-3pg3
CVSS 4.0
1.3 LowCVSS: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:U
Weakness
CWE-116
Updated
2026-11-02
NVD 5.1

Twig is a template language for PHP. Prior to 3.26.0, several filters in twig/markdown-extra and twig/cssinliner-extra are registered with is_safe => [all], causing Twig to treat plain text or HTML output as safe in HTML, JavaScript, CSS, URL, and other contexts where the output is not properly escaped. This issue is fixed in version 3.26.0.

Record
CVE-2026-46637
CVSS 4.0
5.1 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/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
CVSS 3.1
5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Weakness
CWE-116, CWE-79
Updated
2026-11-02
OSV 5.1

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

Twig is a template language for PHP. Prior to 3.26.0, several filters in twig/markdown-extra and twig/cssinliner-extra are registered with is_safe => [all], causing Twig to treat plain text or HTML output as safe in HTML, JavaScript, CSS, URL, and other contexts where the output is not properly escaped. This issue is fixed in version 3.26.0.

Record
CVE-2026-46637
CVSS 4.0
5.1 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Weakness
CWE-116
Updated
2026-11-02
OSVDEBIAN-CVE-2026-46637 5.4

Twig is a template language for PHP. Prior to 3.26.0, several filters in twig/markdown-extra and twig/cssinliner-extra are registered with is_safe => [all], causing Twig to treat plain text or HTML output as safe in HTML, JavaScript, CSS, URL, and other contexts where the output is not properly escaped. This issue is fixed in version 3.26.0.

Record
DEBIAN-CVE-2026-46637
CVSS 3.1
5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Updated
2026-11-02
OSVGHSA-jv8m-2544-3pg3 1.3

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

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>&lt;img src=x onerror=alert(1)&gt;</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.

Record
GHSA-jv8m-2544-3pg3
CVSS 4.0
1.3 LowCVSS: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:U
Weakness
CWE-116
Updated
2026-11-02
OSVUBUNTU-CVE-2026-46637 5.1

Twig is a template language for PHP. Prior to 3.26.0, several filters in twig/markdown-extra and twig/cssinliner-extra are registered with is_safe => [all], causing Twig to treat plain text or HTML output as safe in HTML, JavaScript, CSS, URL, and other contexts where the output is not properly escaped. This issue is fixed in version 3.26.0.

Record
UBUNTU-CVE-2026-46637
CVSS 4.0
5.1 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
CVSS 3.1
5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
twig/markdown-extra
Packagist
 before 3.26.0
3.26.0
twig/cssinliner-extra
Packagist
 before 3.26.0
3.26.0
php-twig
Debian:12
 before 3.5.1-1+deb12u3, plus listed versions
3.5.1-13.5.1-1+deb12u13.5.1-1+deb12u2
3.5.1-1+deb12u3
php-twig
Debian:13
 before 3.27.0-0+deb13u1, plus listed versions
3.20.0-23.21.1-13.21.1-23.21.1-33.22.0-1
Show 11 moreShow less
3.22.0-23.22.1-13.22.1-23.22.1-33.22.2-13.22.2-23.23.0-13.23.0-23.24.0-13.26.0-0+deb13u13.26.0-1
3.27.0-0+deb13u1
php-twig
Debian:14
 before 3.26.0-1, plus listed versions
3.20.0-23.21.1-13.21.1-23.21.1-33.22.0-1
Show 9 moreShow less
3.22.0-23.22.1-13.22.1-23.22.1-33.22.2-13.22.2-23.23.0-13.23.0-23.24.0-1
3.26.0-1
twig/markdown-extra
Packagist
 before 3.26.0, plus listed versions
v2.12.0v2.12.1v2.12.2v2.12.3v2.12.4
Show 45 moreShow less
v2.12.5v2.13.0v2.13.1v2.14.0v2.14.1v2.14.11v2.14.2v2.14.3v2.14.5v2.14.7v2.14.8v2.14.9v2.15.0v2.15.4v2.15.5v2.15.6v2.16.0v3.0.0v3.0.0-BETA1v3.0.1v3.0.2v3.0.3v3.0.4v3.0.5v3.1.0v3.1.1v3.10.0v3.11.0v3.12.0v3.13.0v3.15.0v3.16.0v3.17.0v3.18.0v3.19.0v3.2.1v3.20.0v3.21.0v3.22.0v3.23.0v3.24.0v3.3.0v3.3.1v3.3.3v3.3.4
3.26.0
twig/cssinliner-extra
Packagist
 before 3.26.0, plus listed versions
v2.12.0v2.12.1v2.12.2v2.12.3v2.12.4
Show 45 moreShow less
v2.12.5v2.13.0v2.13.1v2.14.0v2.14.1v2.14.2v2.14.3v2.14.7v2.14.8v2.14.9v2.15.0v2.15.5v2.15.6v2.16.0v3.0.0v3.0.0-BETA1v3.0.1v3.0.2v3.0.3v3.0.4v3.0.5v3.1.0v3.1.1v3.10.0v3.11.0v3.12.0v3.13.0v3.15.0v3.16.0v3.17.0v3.18.0v3.19.0v3.2.1v3.20.0v3.21.0v3.22.0v3.23.0v3.24.0v3.3.0v3.3.3v3.3.4v3.3.5v3.4.0v3.5.0v3.5.1
3.26.0
php-twig
Ubuntu:Pro:20.04:LTS
 All versions, plus listed versions
2.11.3-22.12.1-12.12.2-12.12.3-12.12.5-12.12.5-1ubuntu0.1~esm12.12.5-1ubuntu0.1~esm2
 None known
php-twig
Ubuntu:Pro:22.04:LTS
 All versions, plus listed versions
3.3.2-1ubuntu33.3.4-13.3.6-13.3.7-13.3.8-2ubuntu43.3.8-2ubuntu4+esm13.3.8-2ubuntu4+esm2
 None known
php-twig
Ubuntu:Pro:24.04:LTS
 All versions, plus listed versions
3.7.0-13.7.1-13.8.0-23.8.0-2ubuntu0.1~esm13.8.0-2ubuntu13.8.0-2ubuntu1+esm1
 None known
php-twig
Ubuntu:25.10
 All versions, plus listed versions
3.20.0-2ubuntu1
 None known
php-twig
Ubuntu:26.10
 All versions, plus listed versions
3.23.0-2build73.27.1-13.28.0-1
 None known
php-twig
Ubuntu:Pro:26.04:LTS
 All versions, plus listed versions
3.20.0-2ubuntu13.23.0-2build53.23.0-2build73.23.0-2ubuntu0.1~esm1
 None known

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-46637 is a medium vulnerability (CVSS 5.1) in Symfony Twig, published May 21, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.30%, the 23rd percentile. Fixed in twig/markdown-extra 3.26.0.

References

Show 9 moreShow less
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Left out here: 15 versions. The JSON record has them.

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