ImageMagick is a software suite to create, edit, compose, or convert bitmap images. In versions 7.1.2-9 and prior, the TIM (PSX TIM) image parser contains a critical integer overflow vulnerability in its ReadTIMImage function (coders/tim.c). The code reads width and height (16-bit values) from the file header and calculates image_size = 2 * width * height without checking for overflow. On 32-bit systems (or where size_t is 32-bit), this calculation can overflow if width and height are large (e.g., 65535), wrapping around to a small value. This results in a small heap allocation via AcquireQuantumMemory and later operations relying on the dimensions can trigger an out of bounds read. This issue is fixed in version 7.1.2-10.
Weakness
The product reads data past the end, or before the beginning, of the intended buffer.
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.
- To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.
References