On Debian, Ubuntu, and derivative Linux distributions, an on-path attacker who can manipulate the HTTP traffic (including a malicious mirror or proxy) between an APT client and an archive server triggered by a package install can trick the client into installing an attacker-controlled unverified package and achieve remote code execution with root privileges.
The vulnerability is caused by the reuse of hard links and requires the client to follow redirects and retry the download of package files. It requires the client to have a non-zero Acquire::Retries configuration setting; the value 3 is the default starting with Debian 12 (bookworm) and Ubuntu 22.04 LTS (Jammy Jellyfish), so older releases are unaffected in a default configuration
Weakness
The product, when opening a file or directory, does not sufficiently account for when the name is associated with a hard link to a target that is outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Apt | Ubuntu | devel | * |
| Apt | Ubuntu | esm-infra-legacy/trusty | * |
| Apt | Ubuntu | esm-infra-legacy/xenial | * |
| Apt | Ubuntu | esm-infra/bionic | * |
| Apt | Ubuntu | esm-infra/focal | * |
| Apt | Ubuntu | jammy | * |
| Apt | Ubuntu | noble | * |
| Apt | Ubuntu | resolute | * |
| Apt | Ubuntu | stonking | * |
Potential Mitigations
- Follow the principle of least privilege when assigning access rights to entities in a software system.
- Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.