MEDIUM 5.9 Microsoft PoC

CVE-2023-48795

The SSH transport protocol with certain OpenSSH extensions found in OpenSSH before 9.6 and other products allows remote attackers to bypass integrity checks such that some packets are omitted (from the extension negotiation message) and a client and server may consequently end up with a connection for which some security features have been downgraded or disabled aka a Terrapin attack. This occurs because the SSH Binary Packet Protocol (BPP) implemented by these extensions mishandles the handshake phase and mishandles use of sequence numbers. For example there is an effective attack against SSH's use of ChaCha20-Poly1305 (and CBC with Encrypt-then-MAC). The bypass occurs in chacha20-poly1305@openssh.com and (if CBC is used) the -etm@openssh.com MAC algorithms. This also affects Maverick Synergy Java SSH API before 3.1.0-SNAPSHOT Dropbear through 2022.83 Ssh before 5.1.1 in Erlang/OTP PuTTY before 0.80 AsyncSSH before 2.14.2 golang.org/x/crypto before 0.17.0 libssh before 0.10.6 libssh2

Microsoft Security Update 2023-Dec: The SSH transport protocol with certain OpenSSH extensions found in OpenSSH before 9.6 and other products allows remote attackers to bypass integrity checks such that some packets are omitted (from the extension negotiation message) and a client and server may consequently end up with a connection for which some security features have been downgraded or disabled aka a Terrapin attack. This occurs because the SSH Binary Packet Protocol (BPP) implemented by these extensions mishandles the handshake phase and mishandles use of sequence numbers. For example there is an effective attack against SSH's use of ChaCha20-Poly1305 (and CBC with Encrypt-then-MAC). The bypass occurs in chacha20-poly1305@openssh.com and (if CBC is used) the -etm@openssh.com MAC algorithms. This also affects Maverick Synergy Java SSH API before 3.1.0-SNAPSHOT Dropbear through 2022.83 Ssh before 5.1.1 in Erlang/OTP PuTTY before 0.80 AsyncSSH before 2.14.2 golang.org/x/crypto before 0.17.0 libssh before 0.10.6 libssh2

Affected Products

References

Published: 2023-12-12 · Source: Microsoft · Feed updated: 2026-09-03
This medium severity vulnerability with a CVSS score of 5.9 was published on 2023-12-12 via Microsoft. 🚨 A public proof-of-concept exploit is available on GitHub. EPSS score: 93.3% (top 0% of all CVEs by exploitation probability). Affected: azl3 cf-cli 8.7.3-6 on Azure Linux 3.0, azl3 kubevirt 1.2.0-17 on Azure Linux 3.0, azl3 libssh 0.10.5-2 on Azure Linux 3.0 and 5 more.
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