5.4

CVE-2026-27902: Svelte Vulnerable to XSS via HTML Comment Injection in SSR Error Boundary Hydration Markers

Analyzed
AliasesGHSA-qgvg-pr8v-6rr3
Published 26-02-2026Last modified 26-02-2026

Vulnerability summary

CVE-2026-27902 is a medium (CVSS 5.4) vulnerability in svelte. EPSS estimates a 0.27% chance of exploitation in the next 30 days, higher than 19.5% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.3, 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
0.27%
0%100%
Low · -0.12 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Timeline

  1. 26-02-2026
    PublishedVulnerability first disclosed.
  2. 26-02-2026
    Last modifiedVulnerability information updated.

Description

Svelte performance oriented web framework. Prior to version 5.53.5, errors from `transformError` were not correctly escaped prior to being embedded in the HTML output, causing potential HTML injection and XSS if attacker-controlled content is returned from `transformError`. Version 5.53.5 fixes the issue.

CVSS metrics

4 scores · 3 sources · 2 versions

EPSS trend

Probability

0.27%

Chance of exploitation in the next 30 days

Percentile

20%

Versus all other CVEs

30-day change

Decrease -0.12 pp

From 0.39% 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, no authentication, user interaction (CVSS vector). Other conditions: not stated in public data.

Npm1 product
  • svelte≥ 5.53.0, < 5.53.5
Svelte1 product
Sveltejs1 product

3 vendors · 3 products

References

6 links