CVE-2024-47174

CVE-2024-47174 is a medium-severity vulnerability with a CVSS 3.x base score of 5.9. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-287.

Key facts

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.

Frequently asked questions

What is CVE-2024-47174?
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.
How severe is CVE-2024-47174?
CVE-2024-47174 has a CVSS 3.x base score of 5.9, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2024-47174 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (21st percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2024-47174?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2024-47174 have an EU (EUVD) identifier?
Yes. CVE-2024-47174 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2024-42296.
When was CVE-2024-47174 published?
CVE-2024-47174 was published on 2024-09-26 and last updated on 2026-06-17.

References

Other CWE-287 (Improper Authentication) vulnerabilities

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