Cache poisoning in @sveltejs/adapter-vercel

Description

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.

Basic information

Type
reviewed
Severity
medium
Advisory on GitHub
Open advisory ↗
Repository advisory
Open repository advisory ↗
Source code
Browse source ↗
Published (advisory)
2026-02-19 15:18:02 UTC
Updated
2026-02-23 22:21:40 UTC
GitHub reviewed
2026-02-19 15:18:02 UTC
NVD published
2026-02-20

EPSS Score

Score Percentile
0.01% 0.88%

CVSS Scores

Base score Version Severity Vector
5.3 4.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network.
Attack complexity (AC:L)
Exploitation conditions are straightforward and stable.
Attack requirements (AT:N)
No additional preconditions are required beyond normal reachability.
Privileges required (PR:N)
No privileges are required.
User interaction (UI:P)
A user has to participate (for example click/open/approve).
Vulnerable system confidentiality impact (VC:L)
Limited confidentiality impact on the vulnerable system.
Vulnerable system integrity impact (VI:N)
No integrity impact on the vulnerable system.
Vulnerable system availability impact (VA:N)
No availability impact on the vulnerable system.
Subsequent system confidentiality impact (SC:N)
No confidentiality impact on subsequent systems.
Subsequent system integrity impact (SI:N)
No integrity impact on subsequent systems.
Subsequent system availability impact (SA:N)
No availability impact on subsequent systems.

Identifiers

CWEs

CWE id Name
CWE-346 Origin Validation Error

Credits

  • elliott-with-the-longest-name-on-github (remediation_developer)

Affected packages (1)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
npm @sveltejs/adapter-vercel < 6.3.2 6.3.2

References

cvelogic Threat Intelligence