# CVE-2026-126362: Astro: Reflected XSS via unescaped slot names in @astrojs/svelte

Status: published. Published: 2026-11-12. Updated: 2026-11-12.

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.

## Remediation

- fix: @astrojs/svelte (npm): OSV reports a fixed version 9.1.2. Check the advisory for supported release branches. (source: OSV GHSA-f4j9-crrj-867q) — https://github.com/advisories/GHSA-f4j9-crrj-867q

## Affected products and versions

- withastro / astro: >= 5.7.3, < 9.1.2 (affected). Source: CNA: GitHub_M
-  / @astrojs/svelte (@astrojs/svelte): ≥ 5.7.3; < 9.1.2 (affected, semver); OSV events: introduced 5.7.3; fixed 9.1.2. Source: OSV GHSA-f4j9-crrj-867q

## Severity and prioritization

- CVSS 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; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-79

## 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-867q (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/withastro/astro/commit/5e476365378e41aa2745d003b2383d02008d7b44 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/withastro/astro/releases/tag/@astrojs/svelte@9.1.2 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/advisories/GHSA-f4j9-crrj-867q (OSV / GitHub Security Advisories; advisory)

- https://osv.dev/vulnerability/GHSA-f4j9-crrj-867q (OSV / GitHub Security Advisories; osv)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-126362; retrieved 2026-11-12; source updated 2026-11-12

- OSV / GitHub Security Advisories: https://osv.dev/vulnerability/GHSA-f4j9-crrj-867q; retrieved 2026-11-12; source updated 2026-11-12

Revision: 4028f1c0687481f3724cc5fa36e14f71d224831fc524917b65d4877fde576e7c

Canonical: https://y2.dev/cve/CVE-2026-126362

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