Vulnerability Description
Zydis is an x86/x86-64 disassembler library. Users of Zydis versions v3.2.0 and older that use the string functions provided in `zycore` in order to append untrusted user data to the formatter buffer within their custom formatter hooks can run into heap buffer overflows. Older versions of Zydis failed to properly initialize the string object within the formatter buffer, forgetting to initialize a few fields, leaving their value to chance. This could then in turn cause zycore functions like `ZyanStringAppend` to make incorrect calculations for the new target size, resulting in heap memory corruption. This does not affect the regular uncustomized Zydis formatter, because Zydis internally doesn't use the string functions in zycore that act upon these fields. However, because the zycore string functions are the intended way to work with the formatter buffer for users of the library that wish to extend the formatter, we still consider this to be a vulnerability in Zydis. This bug is patched starting in version 3.2.1. As a workaround, users may refrain from using zycore string functions in their formatter hooks until updating to a patched version.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Zyantific | Zydis | <= 3.2.0 |
Related Weaknesses (CWE)
References
- https://github.com/zyantific/zydis/commit/55dd08c210722aed81b38132f5fd4a04ec1943PatchThird Party Advisory
- https://github.com/zyantific/zydis/security/advisories/GHSA-q42v-hv86-3m4gThird Party Advisory
- https://huntr.dev/bounties/96b0a482-7041-45b1-9327-c6a4a8f32d3aExploitThird Party Advisory
- https://huntr.dev/bounties/d2536d7d-36ce-4723-928c-98d1ee039784ExploitPatchThird Party Advisory
- https://github.com/zyantific/zydis/commit/55dd08c210722aed81b38132f5fd4a04ec1943PatchThird Party Advisory
- https://github.com/zyantific/zydis/security/advisories/GHSA-q42v-hv86-3m4gThird Party Advisory
- https://huntr.dev/bounties/96b0a482-7041-45b1-9327-c6a4a8f32d3aExploitThird Party Advisory
- https://huntr.dev/bounties/d2536d7d-36ce-4723-928c-98d1ee039784ExploitPatchThird Party Advisory
FAQ
What is CVE-2021-41253?
CVE-2021-41253 is a vulnerability with a CVSS score of 5.9 (MEDIUM). Zydis is an x86/x86-64 disassembler library. Users of Zydis versions v3.2.0 and older that use the string functions provided in `zycore` in order to append untrusted user data to the formatter buffer ...
How severe is CVE-2021-41253?
CVE-2021-41253 has been rated MEDIUM with a CVSS base score of 5.9/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2021-41253?
Check the references section above for vendor advisories and patch information. Affected products include: Zyantific Zydis.