CVE-2021-3634

 

Published at: - 31-08-2021 07:15

Last modified: - 16-11-2022 04:31

Total changes: - 14

Description

A flaw has been found in libssh in versions prior to 0.9.6. The SSH protocol keeps track of two shared secrets during the lifetime of the session. One of them is called secret_hash and the other session_id. Initially, both of them are the same, but after key re-exchange, previous session_id is kept and used as an input to new secret_hash. Historically, both of these buffers had shared length variable, which worked as long as these buffers were same. But the key re-exchange operation can also change the key exchange method, which can be based on hash of different size, eventually creating "secret_hash" of different size than the session_id has. This becomes an issue when the session_id memory is zeroed or when it is used again during second key re-exchange.

Common Vulnerability Scoring System (CVSS)

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

 

Verification logic

 

Reference

• https://bugzilla.redhat.com/show_bug.cgi?id=1978810
• DSA-4965-Third Party Advisory
• FEDORA-2021-ec797b6a96-Mailing List, Third Party Advisory
• FEDORA-2021-288925ac19-Mailing List, Third Party Advisory
• https://security.netapp.com/advisory/ntap-20211004-0003/
• FEDORA-2021-f2a020a065-Mailing List, Third Party Advisory
• https://www.oracle.com/security-alerts/cpujan2022.html

 

Keywords

NVD

 

CVE-2021-3634

 

CVE

 

Common vulnerabilities & exposures

 

CVSS

 

Common vulnerability scoring system

 

Security

 

Vulnerabilities

 

Exposures