A vulnerability in the CivetWeb librarys function mg_handle_form_request allows remote attackers to trigger a denial of service (DoS) condition. By sending a specially crafted HTTP POST request containing a null byte in the payload, the server enters an infinite loop during form data parsing. Multiple malicious requests will result in complete CPU exhaustion and render the service unresponsive to further requests.
This issue was fixed in commit 782e189. This issue affects only the library, standalone executable pre-built by vendor is not affected.
Weakness
The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes NUL characters or null bytes when they are sent to a downstream component.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Red Hat Advanced Cluster Security 4.7 | RedHat | advanced-cluster-security/rhacs-collector-rhel8:sha256:488e7716dc50df623f9088ee36120266d4db2637e2d2ce89810f1fdd8f2161f0 | * |
| Red Hat Advanced Cluster Security 4.8 | RedHat | advanced-cluster-security/rhacs-collector-rhel8:sha256:d32b4648796a4cb84487b87c122e881b0b44120cbc4487644de3d282e04b1696 | * |
| Red Hat Advanced Cluster Security 4.9 | RedHat | advanced-cluster-security/rhacs-collector-rhel8:sha256:bb30abe978ff9a89ef5f954d26a2536a40327f2d40bc58a75287eeb9a17e9cca | * |
| Civetweb | Ubuntu | plucky | * |
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.