— Unscored

SvelteKit : XSS via untrusted cache-control header in prerendered page

CVE-2026-114061

Impact Applications that prerender pages and use setHeaders to set a cache-control header from an untrusted source are vulnerable to cross-site scripting (XSS). SvelteKit inserts the header value into a tag without escaping it. An attacker who can influence this value at prerender time can break out of the content attribute and inject HTML or JavaScript into the generated page. The injected code can then execute when users visit the page. Patches The fix escapes the header value before inserting it into the generated HTML. Upgrade to @sveltejs/kit version 3.0.0 or later. Workarounds Avoid forwarding untrusted cache-control header values with setHeaders on prerendered pages. Use a fixed, trusted cache policy instead.

Assessment

CVSS: Not yet scored
Severity: Unscored
EPSS: 0.00213% chance of exploitation in the next 30 days
Known exploited: Not listed in CISA KEV
Exploit availability: Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published: 23 October 2026
Last updated: 23 October 2026
Affected: npm · @sveltejs/kit
Weakness: CWE-79

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