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Low, CVSS 2.3amended

Astro: Arbitrary CSS injection in Astro View Transitions

CVE-2026-114127GHSA-mpr7-6m5w-76rw

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (astro 7.3.3), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • npm astro

    Affected
    >= 7.1.0, <= 7.3.2
    Fixed in
    7.3.3

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
2.3 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N · score source
EPSS
  • CVE-2026-114127: 0.50% estimated exploitation activity in the next 30 days; percentile 42.79 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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 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 inside the generated <style 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…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 5 · amended ·

    Amended from ghsa record GHSA-mpr7-6m5w-76rw

  2. Revision 4 · amended ·

    Amended from ghsa record GHSA-mpr7-6m5w-76rw

  3. Revision 3 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  4. Revision 2 · amended ·

    Amended from osv record GHSA-mpr7-6m5w-76rw

  5. Revision 1 · created ·

    Published from ghsa record GHSA-mpr7-6m5w-76rw

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-114127

Advisory: Astro: Arbitrary CSS injection in Astro View Transitions
IDs: CVE-2026-114127, GHSA-mpr7-6m5w-76rw
Record: https://patchnext.com/advisories/cve-2026-114127 (revision 5, source checked 26 Oct 2026, 13:07 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: astro 7.3.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm astro: affected >= 7.1.0, <= 7.3.2; fixed in 7.3.3

## Suggested inspection (read-only)
- `npm ls astro --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on astro.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-mpr7-6m5w-76rw (GitHub-reviewed advisory GHSA-mpr7-6m5w-76rw lists affected ranges: npm astro >=7.1.0 <=7.3.2)
- Verified: https://osv.dev/vulnerability/GHSA-mpr7-6m5w-76rw (OSV record GHSA-mpr7-6m5w-76rw lists affected ranges: npm astro >=7.1.0 <7.3.3 (fixed))

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