It was discovered that read_file() in apport/hookutils.py would follow symbolic links or open FIFOs. When this function is used by the xorg-hwe-18.04 package apport hooks, it could expose private data to other local users.
Weakness
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Ubuntu_linux | Canonical | 18.04 (including) | 18.04 (including) |
| Ubuntu_linux | Canonical | 20.04 (including) | 20.04 (including) |
| Ubuntu_linux | Canonical | 20.10 (including) | 20.10 (including) |
| Ubuntu_linux | Canonical | 21.04 (including) | 21.04 (including) |
| Ubuntu_linux | Canonical | 21.10 (including) | 21.10 (including) |
| Apport | Ubuntu | bionic | * |
| Apport | Ubuntu | devel | * |
| Apport | Ubuntu | esm-infra-legacy/trusty | * |
| Apport | Ubuntu | esm-infra/bionic | * |
| Apport | Ubuntu | esm-infra/focal | * |
| Apport | Ubuntu | esm-infra/xenial | * |
| Apport | Ubuntu | focal | * |
| Apport | Ubuntu | groovy | * |
| Apport | Ubuntu | hirsute | * |
| Apport | Ubuntu | impish | * |
| Apport | Ubuntu | jammy | * |
| Apport | Ubuntu | trusty | * |
| Apport | Ubuntu | trusty/esm | * |
| Apport | Ubuntu | xenial | * |
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.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/132.html
- https://cwe.mitre.org/data/definitions/17.html
- https://cwe.mitre.org/data/definitions/35.html
- https://cwe.mitre.org/data/definitions/76.html