Vulnerability · Published Jun 22, 2026 · Assigned by VulnCheck

CVE-2026-56306Capgo - Subkey Enforcement Bypass via x-limited-key-id Header Parsing

Medium 6.4

In plain English

A medium-severity improper input validation in Capgo from Capgo. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 23% of all known vulnerabilities).

Severity (CVSS 3.1)6.4Medium

Exploit odds (30 days)0.3%top 76.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

Capgo before 12.128.2 contains a weak parsing vulnerability in the x-limited-key-id header that allows attackers to bypass subkey enforcement by submitting malformed values, zero, or duplicate headers that result in NaN or falsy values. Remote attackers can manipulate the x-limited-key-id header to disable limited key scoping and execute requests using the main API key context instead of restricted subkey permissions.

Affected products (as reported)

Vendor	Product	Versions
Capgo	Capgo	0 – before 12.128.2

Weakness: CWE-20 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

References

GitHub Security Advisory (GHSA-42vv-8j94-24wj) vendor-advisory
VulnCheck Advisory: Capgo - Subkey Enforcement Bypass via x-limited-key-id Header Parsing third-party-advisory