Uncontrolled Resource Consumption

Summary

jsdiff is a JavaScript text differencing implementation. Prior to versions 4.0.3, 5.x prior to 5.2.1 and 6.x through 8.x prior to 8.0.3, attempting to parse a patch whose filename headers contain the line break characters `\r`, `\u2028`, or `\u2029` can cause the `parsePatch` method to enter an infinite loop. It then consumes memory without limit until the process crashes due to running out of memory. Applications are therefore likely to be vulnerable to a denial-of-service attack if they call `parsePatch` with a user-provided patch as input. A large payload is not needed to trigger the vulnerability, so size limits on user input do not provide any protection. Furthermore, some applications may be vulnerable even when calling `parsePatch` on a patch generated by the application itself if the user is nonetheless able to control the filename headers (e.g. by directly providing the filenames of the files to be diffed). The `applyPatch` method is similarly affected if (and only if) called with a string representation of a patch as an argument, since under the hood it parses that string using `parsePatch`. Other methods of the library are unaffected. Finally, a second and lesser interdependent bug - a ReDOS - also exhibits when those same line break characters are present in a patch's *patch* header (also known as its "leading garbage"). A maliciously-crafted patch header of length *n* can take `parsePatch` O(*n*) time to parse. Versions 8.0.3, 5.2.1, and 4.0.3 contain a fix. As a workaround, do not attempt to parse patches that contain any of these characters: `\r`, `\u2028`, or `\u2029`.