GitHub Advisoryadvisory · npm

GHSA-pr6f-5x2q-rwfp Svelte SSR vulnerable to cross-site scripting via spread attributes

MEDIUM Published 2026-05-14 Modified 2026-06-09 Official page ↗
Aliases
CVE-2026-42599
Ecosystem
npm
Packages
svelte
Severity
Moderate
CVSS vector
CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
Weaknesses
CWE-79
Reviewed
2026-05-14

Affected packages

• npm svelte: < 5.55.7 → fixed in 5.55.7

Description

When using spread syntax to render attributes from untrusted data, event handler properties are included in the rendered HTML output. If an application spreads user-controlled or external data as element attributes, an attacker can inject malicious event handlers that execute in victims' browsers. Note that this vulnerability _only_ triggers if the user's browser has JavaScript enabled but Svelte's hydration mechanism does not reach the vulnerable element before the event fires. This is similar to but different from CVE-2026-27121.

Related

Alias · CVE (1)

  • CVE-2026-42599 Svelte is a performance oriented web framework. vulnerability

Weakness · CWE (1)

  • CWE-79 Improper Neutralization of Input During Web Page Generation weakness

References