5.3

CVE-2026-27118: Cache poisoning in @sveltejs/adapter-vercel

Deferred
AliasesGHSA-9pq4-5hcf-288c
Published 20-02-2026Last modified 24-02-2026

Vulnerability summary

CVE-2026-27118 is a medium (CVSS 5.3) Origin Validation Error vulnerability in sveltejs kit. EPSS estimates a 0.28% chance of exploitation in the next 30 days, higher than 20% 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
5.3/10
010
Medium · v4.0 (CVE.org)
EPSS score
0.28%
0%100%
Low · +0.05 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Timeline

  1. 20-02-2026
    PublishedVulnerability first disclosed.
  2. 24-02-2026
    Last modifiedVulnerability information updated.

Description

SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. Versions of @sveltejs/adapter-vercel prior to 6.3.2 are vulnerable to cache poisoning. An internal query parameter intended for Incremental Static Regeneration (ISR) is accessible on all routes, allowing an attacker to cause sensitive user-specific responses to be cached and served to other users. Successful exploitation requires a victim to visit an attacker-controlled link while authenticated. Existing deployments are protected by Vercel's WAF, but users should upgrade as soon as possible. This vulnerability is fixed in 6.3.2.

CVSS metrics

3 scores · 3 sources · 1 version

EPSS trend

Probability

0.28%

Chance of exploitation in the next 30 days

Percentile

20%

Versus all other CVEs

30-day change

Increase +0.05 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, no authentication, user interaction (CVSS vector). Other conditions: not stated in public data.

@sveltejs1 product
  • adapter-vercel< 6.3.2
Sveltejs1 product

2 vendors · 2 products

References

3 links