Summary
webhookd: Unrestricted HTTP Header to Shell Variable Injection
Description
Before 1.22, if the Basic Auth (htpasswd) middleware was not configured, all incoming HTTP headers were blindly forwarded to the webhook script execution environment as shell variables. While the Basic Auth middleware correctly strips the authentication header (X-WebAuthn-User) from the incoming request before conditionally re-injecting it on successful authentication, disabling Basic Auth left the system vulnerable if deployed behind an unhardened reverse proxy.
Mitigation
The WHD_ALLOWED_UPSTREAM_HEADERS configuration setting has been introduced to enforce a strict allowlist of HTTP headers that can be converted into shell variables.
Additionally, the default behavior has been changed to adhere to the principle of least privilege. It is no longer * (allow all). The default allowed headers are now restricted to standard operational headers:Accept,Content-Type,Content-Length,User-Agent,X-Forwarded-For
Administrators relying on upstream authentication proxies must explicitly add their authentication headers (e.g., WHD_ALLOWED_UPSTREAM_HEADERS="Accept,Content-Type,Content-Length,User-Agent,X-Forwarded-For,x-webauthn-user") to ensure they are passed to the scripts securely.
Impact
If an upstream reverse proxy is not properly hardened to strip client-provided authentication headers, an attacker could manually supply these headers (e.g., X-WebAuthn-User). A webhook script relying on this forwarded header for privilege elevation or identity verification could therefore be exploited to bypass security controls and impersonate other users.
CVE-2026-59157 has a CVSS score of 6.5 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.22.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-59157? CVE-2026-59157 is a medium-severity security vulnerability in github.com/ncarlier/webhookd (go), affecting versions < 1.22.0. It is fixed in 1.22.0.
- How severe is CVE-2026-59157? CVE-2026-59157 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/ncarlier/webhookd are affected by CVE-2026-59157? github.com/ncarlier/webhookd (go) versions < 1.22.0 is affected.
- Is there a fix for CVE-2026-59157? Yes. CVE-2026-59157 is fixed in 1.22.0. Upgrade to this version or later.
- Is CVE-2026-59157 exploitable, and should I be worried? Whether CVE-2026-59157 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-59157 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-59157? Upgrade
github.com/ncarlier/webhookdto 1.22.0 or later.