CVE-2026-126362
Astro: Reflected XSS via unescaped slot names in @astrojs/svelte
Astro is a web framework for content-driven websites. From 5.7.3 until 9.1.2, the @astrojs/svelte renderer inserted a named slot into the quoted name attribute of an astro-slot wrapper without HTML escaping. Request-controlled slot names containing a quote could terminate the attribute and inject active HTML. Exploitation required a hydrated Svelte component using a client:* directive and dynamic rendering of the attacker-chosen slot; components that did not render that slot emitted only Astro's escaped fallback content. Both server rendering and client-side hydration used the unsafe slot name. This issue is fixed in version 9.1.2.
Fixes and workarounds
Fix
@astrojs/svelte (npm): OSV reports a fixed version 9.1.2. Check the advisory for supported release branches.
Source: OSV GHSA-f4j9-crrj-867qAffected products and versions
| Product | Versions | Authority |
|---|---|---|
| astro withastro |
>= 5.7.3, < 9.1.2 (affected) | CNA: GitHub_M |
@astrojs/svelte@astrojs/svelte
npm |
≥ 5.7.3; < 9.1.2 (affected, semver); OSV events: introduced 5.7.3; fixed 9.1.2Source events (semver)Other versions: unaffected |
OSV GHSA-f4j9-crrj-867q |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 4.0 / 2.3 low |
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N | CNA: GitHub_M |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://github.com/withastro/astro/security/advisories/GHSA-f4j9-crrj-867qCNA: GitHub_M · x_refsource_CONFIRM
- https://github.com/withastro/astro/commit/5e476365378e41aa2745d003b2383d02008d7b44CNA: GitHub_M · x_refsource_MISC
- https://github.com/withastro/astro/releases/tag/@astrojs/[email protected]CNA: GitHub_M · x_refsource_MISC
- https://github.com/advisories/GHSA-f4j9-crrj-867qOSV / GitHub Security Advisories · advisory
- https://osv.dev/vulnerability/GHSA-f4j9-crrj-867qOSV / GitHub Security Advisories · osv
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