wall in util-linux through 2.40, often installed with setgid tty permissions, allows escape sequences to be sent to other users terminals through argv. (Specifically, escape sequences received from stdin are blocked, but escape sequences received from argv are not blocked.) There may be plausible scenarios where this leads to account takeover.
Weakness
The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could be interpreted as escape, meta, or control character sequences when they are sent to a downstream component.
Affected Software
| Name |
Vendor |
Start Version |
End Version |
| Util-linux |
Ubuntu |
devel |
* |
| Util-linux |
Ubuntu |
focal |
* |
| Util-linux |
Ubuntu |
jammy |
* |
| Util-linux |
Ubuntu |
mantic |
* |
| Util-linux |
Ubuntu |
noble |
* |
| Util-linux |
Ubuntu |
oracular |
* |
Potential Mitigations
- Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
References