Cross-Site Scripting (XSS) in astro (CVE-2026-73422)
Summary
Cross-site scripting in astro (CVE-2026-73422). Risk of unauthorized operations or information disclosure. Exploitable via duration. Mitigation: upgrade to 7.1.0 or later.
Original description
The description as published by the source.
Summary
Astro's server-side View Transition CSS generator interpolates animation properties into an inline `` element without escaping them for the CSS and HTML contexts.
An attacker-controlled value passed to an animation property such as duration can contain a `` sequence, terminate the generated style element, and inject arbitrary HTML or JavaScript.
This is similar to GHSA-8hv8-536x-4wqp, but exploits a different injection point: unescaped View Transition animation values in a server-generated `` element rather than an unescaped slot name in a hydration template.
Like GHSA-8hv8-536x-4wqp, exploitation requires an application to pass attacker-controlled data to an Astro API. However, the value is subsequently inserted into the HTML response without context-appropriate escaping by Astro.
Details
packages/astro/src/runtime/server/transition.ts
The generated stylesheet is wrapped in a `` element and marked as HTML-safe:
const css = sheet.toString();
result._metadata.extraHead.push(markHTMLString(`${css}`));
Animation properties are added to the stylesheet without escaping:
if (anim.duration) {
addAnimationProperty(builder, 'animation-duration', toTimeValue(anim.duration));
}
For string values, toTimeValue() returns the input unchanged:
export function toTimeValue(num: number | string) {
return typeof num === 'number' ? num + 'ms' : num;
}
As a result, a duration value containing `` can escape from the generated styl…
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-73422 has been found in astro.
Attackers can target a specific entry point like duration over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade astro to 7.1.0 or later.
If unsure, ask your IT team or search "astro CVE-2026-73422" on the vendor's site.
CVE-2026-73422 (astro) — CWE-79
Attack surface: duration / TransitionAnimation / easing / direction
Patched: 7.1.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Cross-site scripting (XSS) (CWE-79) exists in astro. Attackers reach the vulnerable code path via duration.
Check the vendor advisory for the affected versions of astro. Attack surface: duration / TransitionAnimation / easing / direction.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 7.1.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'astro' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'astro' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
astroを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade astro to 7.1.0ステージング環境で 7.1.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com