CVE-2024-47174 Credential leak when credentials are used with `<nix/fetchurl.nix>`
Man-in-the-middle attackers can leak credentials or inject malicious code via unverified TLS connections in Nix fetchurl operations.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-47174?
CVE-2024-47174 is a medium-severity vulnerability in NixOS nix, published on 26 Sep 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Nix is a package manager for Linux and other Unix systems. Starting in version 1.11 and prior to versions 2.18.8 and 2.24.8, `<nix/fetchurl.nix>` did not verify TLS certificates on HTTPS connections. This could lead to connection details such as full URLs or credentials leaking in case of a man-in-the-middle (MITM) attack. `<nix/fetchurl.nix>` is also known as the builtin derivation builder `builtin:fetchurl`. It's not to be confused with the evaluation-time function `builtins.fetchurl`, which was not affected by this issue. A user may be affected by the risk of leaking credentials if they have a `netrc` file for authentication, or rely on derivations with `impureEnvVars` set to use credentials from the environment. In addition, the commonplace trust-on-first-use (TOFU) technique of updating dependencies by specifying an invalid hash and obtaining it from a remote store was also vulnerable to a MITM injecting arbitrary store objects. This also applied to the impure derivations experimental feature. Note that this may also happen when using Nixpkgs fetchers to obtain new hashes when not using the fake hash method, although that mechanism is not implemented in Nix itself but rather in Nixpkgs using a fixed-output derivation. The behavior was introduced in version 1.11 to make it consistent with the Nixpkgs `pkgs.fetchurl` and to make `<nix/fetchurl.nix>` work in the derivation builder sandbox, which back then did not have access to the CA bundles by default. Nowadays, CA bundles are bind-mounted on Linux. This issue has been fixed in Nix 2.18.8 and 2.24.8. As a workaround, implement (authenticated) fetching with `pkgs.fetchurl` from Nixpkgs, using `impureEnvVars` and `curlOpts` as needed.
Weakness: CWE-287
Which versions are affected by CVE-2024-47174?
How do I fix CVE-2024-47174?
Upgrade to a fixed version.
Is CVE-2024-47174 being exploited?
There is no known exploitation of CVE-2024-47174 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2024-47174, GHSA-6fjr-mq49-mm2c, UBUNTU-CVE-2024-47174.