fish-shop/syntax-check is a GitHub action for syntax checking fish shell files. Improper neutralization of delimiters in the pattern input (specifically the command separator ; and command substitution characters ( and )) mean that arbitrary command injection is possible by modification of the input value used in a workflow. This has the potential for exposure or exfiltration of sensitive information from the workflow runner, such as might be achieved by sending environment variables to an external entity. It is recommended that users update to the patched version v1.6.12 or the latest release version v2.0.0, however remediation may be possible through careful control of workflows and the pattern input value used by this action.
Weakness
The product does not neutralize or incorrectly neutralizes delimiters.
Affected Software
| Name |
Vendor |
Start Version |
End Version |
| Syntax-check |
Fish-shop |
* |
1.6.12 (excluding) |
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