🛡️ CVE-2026-42599 — svelte

🟡 CVSS 6.1 — Medium ✅ No Known Exploit CWE-79 NVD
6.1
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Svelte SSR vulnerable to cross-site scripting via spread attributes

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](https://nvd.nist.gov/vuln/detail/CVE-2026-27121).

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs administrative privileges on the target. No user interaction is required. Rated impact: confidentiality none, integrity none, availability none.

Weakness class

CVE-2026-42599 is classified as CWE-79: Cross-site Scripting (XSS). User-supplied data is written into a page without escaping, so attacker script runs in the browser of anyone who views it.

Affected software

CVE-2026-42599 is recorded against 2 packages.

  • svelte
  • unknown

Timeline and source

Published on 14 May 2026 and last revised on 23 July 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com (Web)
nvd.nist.gov (Advisory)
nvd.nist.gov (Advisory)
github.com (Package)
github.com (Web)

Details

Severity MEDIUM
CVSS Score 6.1
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
CWE CWE-79
Public Exploit ✅ No
Source NVD
Published 2026-05-14
Updated 2026-08-12
Modified 2026-07-23
Fix URL N/A

Affected Packages

Software From version Fixed in
svelte — —
unknown — —

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