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Vulnerabilities

Vulnerability · CVE-2026-114127

Astro: Arbitrary CSS injection in Astro View Transitions

Published Oct 21, 2026 · catalog updated Oct 22, 2026 · Astro: Arbitrary CSS injection

Last checked Oct 25, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-114127. EPSS is 0.39%. Act only if a listed version of Astro: Arbitrary CSS injection is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Astro: Arbitrary CSS injection).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Low2.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.39%
Remediation
Version ranges on file
Affected products
npm astro · package npm · vendor withastro astro

### Summary Astro's server-side View Transition CSS generator did not keep string animation properties within their generated CSS declarations. In an application that passes attacker-controlled data into an animation property such as , a value containing CSS delimiters could terminate the declaration and rule, then add attacker-selected CSS to the server-rendered page. The injected content remains inside the generated element. It cannot terminate that element or inject HTML or JavaScript because Astro escapes before emitting the stylesheet. ### Severity Exploitation requires an application to pass untrusted, request-derived, or user-controlled content directly into a transition animation value. This is an uncommon application pattern, and applications using static or otherwise trusted transition values are unaffected. The resulting capability is limited to CSS in the rendered document. The proof of concept does not demonstrate JavaScript execution, HTML injection, an origin-boundary bypass, or access to server-only data. ### Details Animation values are collected by in and passed to . String values were converted directly with : The animation builder then interpolated each value into a declaration: The completed stylesheet passes through , which escapes literal characters to keep the content inside its HTML element. CSS delimiters such as , , and remained active, allowing a value to escape its intended declaration and add another rule. The shared serializer handles , , , , , and animation names, so custom transition objects using those string properties followed the same path. The fix encodes CSS declaration delimiters while serializing each animation value. Supported CSS functions and strings, including and , remain unchanged. ### Proof of Concept Using , create an on-demand rendered page: Request the page with: Before the fix, the generated stylesheet contains an active rule equivalent to: In Chromium, the target's computed styles change to and . This behavior is

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • npm astro>= 7.1.0, <= 7.3.2
  • package npmversion unspecified
  • vendor withastro astroversion unspecified

How to fix CVE-2026-114127

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-114127. EPSS is 0.39%. Act only if a listed version of Astro: Arbitrary CSS injection is installed.

Which versions are affected?

Compare what you have installed with >= 7.1.0, <= 7.3.2. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-79: Cross-site Scripting (XSS). EPSS 0.39%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 22, 2026 · GitHub Advisory Database

    Detected

    ### Summary Astro's server-side View Transition CSS generator did not keep string animation properties within their generated CSS declarations. In an application that passes attacker-controlled data into an animation property such as , a value containing CSS delimiters could terminate the declaration and rule, then add attacker-selected CSS to the server-rendered page. The injected content remains

  2. Oct 22, 2026 · GitHub Advisory Database

    Updated

    ### Summary Astro's server-side View Transition CSS generator did not keep string animation properties within their generated CSS declarations. In an application that passes attacker-controlled data into an animation property such as , a value containing CSS delimiters could terminate the declaration and rule, then add attacker-selected CSS to the server-rendered page. The injected content remains

Sources

  • CVE.orgVulnerability recordCVE-2026-114127

    Astro is a web framework for content-driven websites. From 7.1.0 until 7.3.3, Astro's server-side View Transition CSS generator does not keep string animation properties within their generated declarations. An application that passes attacker-controlled data into properties such

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-114127

    30-day exploitation probability 0.39%

    first.org
  • GitHub Advisory DatabasePackage advisoryGHSA-mpr7-6m5w-76rw

    Astro: Arbitrary CSS injection in Astro View Transitions

    github.com
  • GitLab Advisory DatabasePackage advisoryCVE-2026-114127

    Astro's server-side View Transition CSS generator did not keep string animation properties within their generated CSS declarations. In an application that passes attacker-controlled data into an animation property such as duration, a value containing CSS delimiters could terminate the declaration and rule, then add attacker-selected CSS to the server-rendered page. The injected content remains ins

    advisories.gitlab.com
  • Snyk Vulnerability DatabasePackage advisorySNYK-JS-ASTRO-21431490

    Cross-site Scripting (XSS)

    security.snyk.io

References

Freshness

Last verified in this catalog Oct 25, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • GitLab Advisory DatabaseOct 25, 2026
  • FIRST EPSSOct 25, 2026
  • Snyk Vulnerability DatabaseOct 25, 2026
  • GitHub Advisory DatabaseOct 23, 2026
  • CVE.orgOct 23, 2026