Описание
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 through 1.11.0, Thorn Tech SFTP Gateway before 3.4.6, Tera Term before 5.1, Paramiko before 3.4.0, jsch before 0.2.15, SFTPGo before 2.5.6, Netgate pfSense Plus through 23.09.1, Netgate pfSense CE through 2.7.2, HPN-SSH through 18.2.0, ProFTPD before 1.3.8b (and before 1.3.9rc2), ORYX CycloneSSH before 2.3.4, NetSarang XShell 7 before Build 0144, CrushFTP before 10.6.0, ConnectBot SSH library before 2.2.22, Apache MINA sshd through 2.11.0, sshj through 0.37.0, TinySSH through 20230101, trilead-ssh2 6401, LANCOM LCOS and LANconfig, FileZilla before 3.66.4, Nova before 11.8, PKIX-SSH before 14.4, SecureCRT before 9.4.3, Transmit5 before 5.10.4, Win32-OpenSSH before 9.5.0.0p1-Beta, WinSCP before 6.2.2, Bitvise SSH Server before 9.32, Bitvise SSH Client before 9.33, KiTTY through 0.76.1.13, the net-ssh gem 7.2.0 for Ruby, the mscdex ssh2 module before 1.15.0 for Node.js, the thrussh library before 0.35.1 for Rust, and the Russh crate before 0.40.2 for Rust.
A flaw was found in the SSH channel integrity. By manipulating sequence numbers during the handshake, an attacker can remove the initial messages on the secure channel without causing a MAC failure. For example, an attacker could disable the ping extension and thus disable the new countermeasure in OpenSSH 9.5 against keystroke timing attacks.
Отчет
This CVE is classified as moderate because the attack requires an active Man-in-the-Middle (MITM) who can intercept and modify the connection's traffic at the TCP/IP layer. Although the attack is cryptographically innovative, its security impact is fortunately quite limited. It only allows the deletion of consecutive messages, and deleting most messages at this protocol stage prevents user authentication from proceeding, leading to a stalled connection. The most significant identified impact is that it enables a MITM to delete the SSH2_MSG_EXT_INFO message sent before authentication begins. This allows the attacker to disable a subset of keystroke timing obfuscation features. However, there is no other observable impact on session secrecy or session integrity.
Меры по смягчению последствий
Update to the last version and check that client and server provide kex pseudo-algorithms indicating usage of the updated version of the protocol which is protected from the attack. If "kex-strict-c-v00@openssh.com" is provided by clients and "kex-strict-s-v00@openssh.com" is in the server's reply, no other steps are necessary. Disabling ciphers if necessary: If "kex-strict-c-v00@openssh.com" is not provided by clients or "kex-strict-s-v00@openssh.com" is absent in the server's reply, you can disable the following ciphers and HMACs as a workaround on RHEL-8 and RHEL-9:
- chacha20-poly1305@openssh.com
- hmac-sha2-512-etm@openssh.com
- hmac-sha2-256-etm@openssh.com
- hmac-sha1-etm@openssh.com
- hmac-md5-etm@openssh.com To do that through crypto-policies, one can apply a subpolicy with the following content:
e.g., by putting these lines into /etc/crypto-policies/policies/modules/CVE-2023-48795.pmod, applying the resulting subpolicy with update-crypto-policies --set $(update-crypto-policies --show):CVE-2023-48795 and restarting openssh server.
One can verify that the changes are in effect by ensuring the ciphers listed above are missing from both /etc/crypto-policies/back-ends/openssh.config and /etc/crypto-policies/back-ends/opensshserver.config.
For more details on using crypto-policies, please refer to https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/9/html/security_hardening/using-the-system-wide-cryptographic-policies_security-hardening
Note that this procedure does limit the interoperability of the host and is only suggested as a temporary mitigation until the issue is fully resolved with an update.
For RHEL-7:
We can recommend to use strict MACs and Ciphers on RHEL7 in both files /etc/ssh/ssh_config and /etc/ssh/sshd_config.
Below strict set of Ciphers and MACs can be used as mitigation for RHEL 7.
- For Openshift Container Platform 4: Please refer the KCS[1] document for verifying the fix in RHCOS. [1] https://access.redhat.com/solutions/7071748
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| cert-manager Operator for Red Hat OpenShift | cert-manager/jetstack-cert-manager-rhel9 | Not affected | ||
| Migration Toolkit for Containers | rhmtc/openshift-migration-velero-rhel8 | Affected | ||
| OpenShift Developer Tools and Services | odo | Fix deferred | ||
| OpenShift Pipelines | openshift-pipelines-client | Affected | ||
| OpenShift Service Mesh 2 | openshift-service-mesh/kiali-rhel8 | Not affected | ||
| Red Hat Advanced Cluster Security 3 | advanced-cluster-security/rhacs-main-rhel8 | Out of support scope | ||
| Red Hat Advanced Cluster Security 3 | advanced-cluster-security/rhacs-scanner-rhel8 | Out of support scope | ||
| Red Hat Advanced Cluster Security 4 | advanced-cluster-security/rhacs-main-rhel8 | Affected | ||
| Red Hat Advanced Cluster Security 4 | advanced-cluster-security/rhacs-scanner-rhel8 | Not affected | ||
| Red Hat Ansible Automation Platform 2 | aap-cloud-metrics-collector-container | Not affected |
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Дополнительная информация
Статус:
EPSS
5.9 Medium
CVSS3
Связанные уязвимости
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...
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.
The SSH transport protocol with certain OpenSSH extensions, found in O ...
EPSS
5.9 Medium
CVSS3