OpenEXR provides the specification and reference implementation of the EXR file format, an image storage format for the motion picture industry. In versions 3.3.0 through 3.3.6 and 3.4.0 through 3.4.4, a heap-buffer-overflow (OOB read) occurs in the istream_nonparallel_read function in ImfContextInit.cpp when parsing a malformed EXR file through a memory-mapped IStream. A signed integer subtraction produces a negative value that is implicitly converted to size_t, resulting in a massive length being passed to memcpy. Versions 3.3.7 and 3.4.5 contain a patch.
Weakness
The product uses a signed primitive and performs a cast to an unsigned primitive, which can produce an unexpected value if the value of the signed primitive can not be represented using an unsigned primitive.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Openexr | Openexr | 3.3.0 (including) | 3.3.7 (excluding) |
| Openexr | Openexr | 3.4.0 (including) | 3.4.5 (excluding) |
Extended Description
It is dangerous to rely on implicit casts between signed and unsigned numbers because the result can take on an unexpected value and violate assumptions made by the program. Often, functions will return negative values to indicate a failure. When the result of a function is to be used as a size parameter, using these negative return values can have unexpected results. For example, if negative size values are passed to the standard memory copy or allocation functions they will be implicitly cast to a large unsigned value. This may lead to an exploitable buffer overflow or underflow condition.