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Bug 2250326 (CVE-2023-46445) - CVE-2023-46445 python-asyncssh: Rogue Extension Negotiation
Summary: CVE-2023-46445 python-asyncssh: Rogue Extension Negotiation
Keywords:
Status: NEW
Alias: CVE-2023-46445
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On: 2255433 2265139 2250327 2250328
Blocks:
TreeView+ depends on / blocked
 
Reported: 2023-11-17 18:22 UTC by Borja Tarraso
Modified: 2024-02-20 16:19 UTC (History)
9 users (show)

Fixed In Version: python-asyncssh 2.14.1
Clone Of:
Environment:
Last Closed:
Embargoed:


Attachments (Terms of Use)

Description Borja Tarraso 2023-11-17 18:22:15 UTC
An issue in AsyncSSH v2.14.0 and earlier allows attackers to control the extension info message (RFC 8308) via a man-in-the-middle attack.

The rogue extension negotiation attack targets an AsyncSSH client connecting to any SSH server sending an extension info message. The attack exploits an implementation flaw in the AsyncSSH implementation to inject an extension info message chosen by the attacker and delete the original extension info message, effectively replacing it.

A correct SSH implementation should not process an unauthenticated extension info message. However, the injected message is accepted due to flaws in AsyncSSH. AsyncSSH supports the server-sig-algs and global-requests-ok extensions. Hence, the attacker can downgrade the algorithm used for client authentication by meddling with the value of server-sig-algs (e.g. use of SHA-1 instead of SHA-2).

Comment 1 Borja Tarraso 2023-11-17 18:22:38 UTC
Created python-asyncssh tracking bugs for this issue:

Affects: epel-8 [bug 2250327]
Affects: fedora-all [bug 2250328]


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