Bug 2048523 (CVE-2016-20012)

Summary: CVE-2016-20012 openssh: Public key information leak
Product: [Other] Security Response Reporter: Pedro Sampaio <psampaio>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED NOTABUG QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: bdettelb, crypto-team, dbelyavs, dwalsh, jburrell, jjelen, kyoshida, lkundrak, mattias.ellert, tm, vkumar, yozone
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Fixed In Version: Doc Type: If docs needed, set a value
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Clone Of: Environment:
Last Closed: 2022-03-16 19:06:38 UTC Type: ---
Regression: --- Mount Type: ---
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Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 2056666, 2056667, 2056817    
Bug Blocks: 2048524    

Description Pedro Sampaio 2022-01-31 12:41:06 UTC 
OpenSSH through 8.7 allows remote attackers, who have a suspicion that a certain combination of username and public key is known to an SSH server, to test whether this suspicion is correct. This occurs because a challenge is sent only when that combination could be valid for a login session.

References:

https://github.com/openssh/openssh-portable/blob/d0fffc88c8fe90c1815c6f4097bc8cbcabc0f3dd/auth2-pubkey.c#L261-L265
https://github.com/openssh/openssh-portable/pull/270
https://rushter.com/blog/public-ssh-keys/
https://utcc.utoronto.ca/~cks/space/blog/tech/SSHKeysAreInfoLeak
Comment 1 juneau 2022-01-31 17:09:58 UTC 
Marking Services affected/delegated for presence of the affected code. Minimal likelihood of exploit.
Comment 4 Marco Benatto 2022-02-21 18:58:12 UTC 
Marking RHEL8 and RHEL9 as delegated as the code is present, however upstream seems to not recognize this as a vulnerability although it has a CVE ID assigned. Also it seems there's no fix present in upstream as the pull request seems to be open and in draft state yet.
Comment 5 Avinash Hanwate 2022-02-22 06:02:42 UTC 
Created openssh tracking bugs for this issue:

Affects: fedora-all [bug 2056817]
Comment 9 Marco Benatto 2022-03-16 19:06:38 UTC 
Closing this as NOTABUG as upstream and Red Hat doesn't consider it to be a security vulnerability.