Strix
26.1K

CVE-2026-27121

MEDIUMCVSS 5.1/10EPSS 0.19%

Last modified

CVE-2026-27121 is a medium-severity vulnerability rated 5.1/10 on the CVSS scale. svelte performance oriented web framework. Versions of svelte prior to 5.51.5 are vulnerable to cross-site scripting (XSS) during server-side rendering. EPSS estimates a 0.19% chance of exploitation in the next 30 days.

Description

svelte performance oriented web framework. Versions of svelte prior to 5.51.5 are vulnerable to cross-site scripting (XSS) during server-side rendering. 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. This vulnerability is fixed in 5.51.5.

Metrics

CVSS 3.1
5.4/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

CVSS 4.0
5.1/10

CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:L/VI:N/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability
0.19%

8.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
SvelteSvelte< 5.51.5

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is CVE-2026-27121?
svelte performance oriented web framework. Versions of svelte prior to 5.51.5 are vulnerable to cross-site scripting (XSS) during server-side rendering. 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. This vulnerability is fixed in 5.51.5.
How severe is CVE-2026-27121?
CVE-2026-27121 has a CVSS score of 5.1/10 (MEDIUM severity). The EPSS model estimates a 0.19% probability of exploitation in the next 30 days.
How do I fix CVE-2026-27121?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-27121?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST