Summary
Chisel's AUTH environment variable not respected in server entrypoint
The Chisel server doesn't ever read the documented AUTH environment variable used to set credentials, which allows any unauthenticated user to connect, even if credentials were set. This advisory is a formalization of a report sent to the maintainer via email.
Details
In the help page for the chisel server subcommand, it mentions an AUTH environment variable that can be set in order to provide credentials that the server should authenticate connections against: https://github.com/jpillora/chisel/blob/3de177432cd23db58e57f376b62ad497cc10840f/main.go#L138.
The issue is that the server entrypoint doesn't ever read the AUTH environment variable. The only place that this happens is in the client entrypoint: https://github.com/jpillora/chisel/blob/3de177432cd23db58e57f376b62ad497cc10840f/main.go#L452
This subverts the expectations set by the documentation, allowing unauthenticated users to connect to a Chisel server, even if auth is attempted to be set up in this manner.
PoC
Run chisel server, first specifying credentials with the AUTH environment variable, then with the --auth argument. In the first case, the server allows connections without authentication, while in the second, the correct behavior is exhibited.
Impact
Anyone who is running the Chisel server, and that is using the AUTH environment variable to specify credentials to authenticate against. Chisel is often used to provide an entrypoint to a private network, which means services that are gated by Chisel may be affected. Additionally, Chisel is often used for exposing services to the internet. An attacker could MITM requests by connecting to a Chisel server and requesting to forward traffic from a remote port.
A critical operation is accessible without requiring any authentication. Typical impact: any user can invoke the privileged function.
CVE-2024-43798 has a CVSS score of 8.6 (High). 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 (1.10.0); 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-2024-43798? CVE-2024-43798 is a high-severity missing authentication for critical function vulnerability in github.com/jpillora/chisel (go), affecting versions < 1.10.0. It is fixed in 1.10.0. A critical operation is accessible without requiring any authentication.
- How severe is CVE-2024-43798? CVE-2024-43798 has a CVSS score of 8.6 (High). 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/jpillora/chisel are affected by CVE-2024-43798? github.com/jpillora/chisel (go) versions < 1.10.0 is affected.
- Is there a fix for CVE-2024-43798? Yes. CVE-2024-43798 is fixed in 1.10.0. Upgrade to this version or later.
- Is CVE-2024-43798 exploitable, and should I be worried? Whether CVE-2024-43798 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-2024-43798 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-2024-43798? Upgrade
github.com/jpillora/chiselto 1.10.0 or later.