CVE-2021-41253 Information

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 Vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Reference

https://huntr.dev/bounties/96b0a482-7041-45b1-9327-c6a4a8f32d3a https://github.com/zyantific/zydis/commit/55dd08c210722aed81b38132f5fd4a04ec1943b5 https://huntr.dev/bounties/d2536d7d-36ce-4723-928c-98d1ee039784 https://github.com/zyantific/zydis/security/advisories/GHSA-q42v-hv86-3m4g

Attack Complexity

HIGH

Privileges Required

NONE

User Interaction Required

NONE

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

HIGH

Availability Impact

HIGH

Base Score

HIGH

Base Severity

8.1