Astro: Reflected XSS via unescaped View Transition animation properties

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-73422
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-12 21:17:41 UTC
Updated2026-08-12 21:17:41 UTC
DescriptionAstro is a web framework for content-driven websites. From 2.9.0 until 7.1.0, Astro's server-side View Transition CSS generator interpolates animation properties into an inline style element without escaping them for CSS and HTML contexts. An attacker-controlled View Transition animation value such as duration can terminate the generated style element and inject arbitrary HTML or JavaScript. The affected code is packages/astro/src/runtime/server/transition.ts; renderTransition passes sheet.toString() into markHTMLString(), while addAnimationProperty serializes duration through toTimeValue() and also handles easing, direction, delay, fillMode, and name. Exploitation requires an on-demand or server-rendered route to pass attacker-controlled data into a View Transition animation definition and can execute arbitrary JavaScript in the affected application's origin, allowing access to sensitive page data and authenticated actions available to the victim. This issue is fixed in version 7.1.0.

Risk And Classification

Primary CVSS: v4.0 5.3 MEDIUM from [email protected]

CVSS: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: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

Problem Types: CWE-79 | CWE-79 CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary5.3MEDIUMCVSS: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:X/C...
4.0CNADECLARED5.3MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
Passive
Confidentiality
None
Integrity
None
Availability
None
Sub Conf.
Low
Sub Integrity
Low
Sub Availability
None

CVSS: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: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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Withastro Astro affected >= 2.9.0, < 7.1.0 Not specified

References

ReferenceSourceLinkTags
github.com/withastro/astro/pull/17393 [email protected] github.com
github.com/withastro/astro/commit/092da560eea77ee63a3e2c583c80d8238544e42b [email protected] github.com
github.com/withastro/astro/releases/tag/[email protected] [email protected] github.com
github.com/withastro/astro/security/advisories/GHSA-4g3v-8h47-v7g6 [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

© CVE.report 2026

Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties, implied or otherwise, with regard to this information or its use. Any use of this information is at the user's risk. It is the responsibility of user to evaluate the accuracy, completeness or usefulness of any information, opinion, advice or other content. EACH USER WILL BE SOLELY RESPONSIBLE FOR ANY consequences of his or her direct or indirect use of this web site. ALL WARRANTIES OF ANY KIND ARE EXPRESSLY DISCLAIMED. This site will NOT BE LIABLE FOR ANY DIRECT, INDIRECT or any other kind of loss.

CVE, CWE, and OVAL are registred trademarks of The MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. This site includes MITRE data granted under the following license.

Free CVE JSON API cve.report/api

CVE.report and Source URL Uptime Status status.cve.report