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CVE-2021-41253 Detail

Current 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.


View Analysis Description

Severity



CVSS 3.x Severity and Metrics:

NIST CVSS score
NIST: NVD
Base Score:  8.1 HIGH
Vector:  CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Nist CVSS score does not match with CNA score
CNA:  GitHub, Inc.
Base Score:  5.9 MEDIUM
Vector:  CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H


NVD Analysts use publicly available information to associate vector strings and CVSS scores. We also display any CVSS information provided within the CVE List from the CNA.

Note: It is possible that the NVD CVSS may not match that of the CNA. The most common reason for this is that publicly available information does not provide sufficient detail or that information simply was not available at the time the CVSS vector string was assigned.

References to Advisories, Solutions, and Tools

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

Weakness Enumeration

CWE-ID CWE Name Source
CWE-457 Use of Uninitialized Variable Provider acceptance level GitHub, Inc.  
CWE-122 Heap-based Buffer Overflow Provider acceptance level GitHub, Inc.  

Known Affected Software Configurations Switch to CPE 2.2

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Change History

1 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2021-41253
NVD Published Date:
11/08/2021
NVD Last Modified:
11/15/2021
Source:
GitHub, Inc.