Information Disclosure via Flags override link

published 2025-05-02 18 mo ago modified 2026-06-17 4 mo ago also GHSA-892p-pqrr-hxqr , EUVD-2025-13288

cvss: 6.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 27%
public exploits: 0; none known

Flags SDK is an open-source feature flags toolkit for Next.js and SvelteKit. Impacted versions include flags from 3.2.0 and prior and @vercel/flags from 3.1.1 and prior as certain circumstances allows a bad actor with detailed knowledge of the vulnerability to list all flags returned by the flags discovery endpoint (.well-known/vercel/flags). This vulnerability allows for information disclosure, where a bad actor could gain access to a list of all feature flags exposed through the flags discovery endpoint, including the flag names, flag descriptions, available options and their labels (e.g. true, false), and default flag values. This issue has been patched in flags@4.0.0, users of flags and @vercel/flags should also migrate to flags@4.0.0.

Patch / fix

fixed in 1

npm flags 4.0.0

CISA SSVC

Exploitation: none
Automatable: yes
Technical impact: partial
Assessed: 18 mo ago (2025-05-02)

Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 27% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
GitHub	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
npm	flags	<4.0.0	4.0.0
npm	@vercel/flags	<=3.1.1	no fix listed

Affected products

vercel flags

Classification

Weakness

CWE-200 Exposure of Sensitive Information to an Unauthorized Actor

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary