5.4

CVE-2026-27121: Svelte affected by cross-site scripting via spread attributes in Svelte SSR

Analyzed
AliasesCGA-688r-vg48-5q7wCGA-r4gf-jc8h-4c5fGHSA-f7gr-6p89-r883
Published 20-02-2026Last modified 23-02-2026

Vulnerability summary

CVE-2026-27121 is a medium (CVSS 5.4) vulnerability in svelte. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 12.6% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.1, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
5.4/10
010
Medium · v3.1 (NVD)
EPSS score
0.22%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 0 · Related 1
CGA-4GXM-66X4-6WR6

Timeline

  1. 20-02-2026
    PublishedVulnerability first disclosed.
  2. 23-02-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

6 scores · 5 sources · 2 versions

EPSS trend

Probability

0.22%

Chance of exploitation in the next 30 days

Percentile

13%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.22% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, administrative account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Chainguard5 products
  • langfuse-2-workerAll versions (No fix recorded)
  • langfuse-3-worker< 3.163.0-r0
  • langfuse-fips-2-workerAll versions (No fix recorded)
  • langfuse-fips-3-worker< 3.163.0-r0
  • langfuse-fips-3.152-workerAll versions (No fix recorded)
Npm1 product
  • svelte< 5.51.5
Svelte1 product
Sveltejs1 product
Wolfi1 product
  • langfuse-3-worker< 3.163.0-r0

5 vendors · 9 products

References

4 links