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.

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.

Summary

Terrapin is a prefix truncation attack targeting the SSH protocol. More precisely, Terrapin breaks the integrity of SSH's secure channel. By carefully adjusting the sequence numbers during the handshake, an attacker can remove an arbitrary amount of messages sent by the client or server at the beginning of the secure channel without the client or server noticing it.

Mitigations

To mitigate this protocol vulnerability, OpenSSH suggested a so-called "strict kex" which alters the SSH handshake to ensure a Man-in-the-Middle attacker cannot introduce unauthenticated messages as well as convey sequence number manipulation across handshakes.

Warning: To take effect, both the client and server must support this countermeasure.

As a stop-gap measure, peers may also (temporarily) disable the affected algorithms and use unaffected alternatives like AES-GCM instead until patches are available.

Details

The SSH specifications of ChaCha20-Poly1305 (chacha20-poly1305@openssh.com) and Encrypt-then-MAC (-etm@openssh.com MACs) are vulnerable against an arbitrary prefix truncation attack (a.k.a. Terrapin attack). This allows for an extension negotiation downgrade by stripping the SSHMSGEXTINFO sent after the first message after SSHMSGNEWKEYS, downgrading security, and disabling attack countermeasures in some versions of OpenSSH. When targeting Encrypt-then-MAC, this attack requires the use of a CBC cipher to be practically exploitable due to the internal workings of the cipher mode. Additionally, this novel attack technique can be used to exploit previously unexploitable implementation flaws in a Man-in-the-Middle scenario.

The attack works by an attacker injecting an arbitrary number of SSHMSGIGNORE messages during the initial key exchange and consequently removing the same number of messages just after the initial key exchange has concluded. This is possible due to missing authentication of the excess SSHMSGIGNORE messages and the fact that the implicit sequence numbers used within the SSH protocol are only checked after the initial key exchange.

In the case of ChaCha20-Poly1305, the attack is guaranteed to work on every connection as this cipher does not maintain an internal state other than the message's sequence number. In the case of Encrypt-Then-MAC, practical exploitation requires the use of a CBC cipher; while theoretical integrity is broken for all ciphers when using this mode, message processing will fail at the application layer for CTR and stream ciphers.

For more details see https://terrapin-attack.com.

Impact

This attack targets the specification of ChaCha20-Poly1305 (chacha20-poly1305@openssh.com) and Encrypt-then-MAC (-etm@openssh.com), which are widely adopted by well-known SSH implementations and can be considered de-facto standard. These algorithms can be practically exploited; however, in the case of Encrypt-Then-MAC, we additionally require the use of a CBC cipher. As a consequence, this attack works against all well-behaving SSH implementations supporting either of those algorithms and can be used to downgrade (but not fully strip) connection security in case SSH extension negotiation (RFC8308) is supported. The attack may also enable attackers to exploit certain implementation flaws in a man-in-the-middle (MitM) scenario.

Rejected reason: This CVE ID has been rejected because it does not describe a security vulnerability.

Rejected reason: This CVE ID has been rejected because it does not describe a security vulnerability.

Rejected reason: This CVE ID has been rejected because it does not describe a security vulnerability.

Netgate AMITI Antivirus build 23.0.305 contains an unquoted service path vulnerability in the AmitiAvSrv and AmitiAntivirusHealth services that allows local attackers to escalate privileges. Attackers can place a malicious executable in the unquoted service path and trigger service restart or system reboot to execute code with LocalSystem privileges.

NETGATE Registry Cleaner build 16.0.205 contains an unquoted service path vulnerability in the NGRegClnSrv service that allows local attackers to escalate privileges by exploiting the service binary path. Attackers can place a malicious executable in the unquoted path and trigger service restart or system reboot to execute code with LocalSystem privileges.

Netgate pfSense CE through 2.9.0 contains an OS command injection vulnerability that allows authenticated users with gateway edit privileges to execute commands as root by injecting shell metacharacters into an IPv6 link-local zone index. Attackers can set a gateway Monitor IP whose unvalidated zone carries a payload, which startdpinger() passes unescaped to the dpinger shell command when monitoring is applied.

pfSense CE 2.4.5 through 2.9.0 contains an OS command injection vulnerability that allows authenticated WebGUI users with Advanced Admin Access privilege to execute commands as root via Login Protection settings. Attackers can submit sshguard threshold, block time, or detection time values containing newlines or $(...) that are written unvalidated to sshguard.conf and sourced as root on restart.

Netgate pfSense CE through 2.9.0 contains a php.ini injection vulnerability that allows authenticated users with General Setup privileges to inject directives by submitting an unvalidated timezone value. Attackers can embed a quote and newline to add autoprependfile pointing at /var/db/zoneinfo, executing PHP as root after php.ini is regenerated at boot or php-fpm restart.

Netgate pfSense CE through 2.9.0 contains a CRLF injection vulnerability in servicesunboundacls.php that allows authenticated users with the DNS Resolver: Access Lists privilege to inject Unbound configuration directives. Attackers can embed CR/LF characters in the aclname or aclaction fields written to accesslists.conf to add local-data, local-zone, or forward-zone directives and control DNS answers served to LAN clients.

Netgate pfSense CE 2.3.0 through 2.9.0 contains a stored cross-site scripting vulnerability that allows authenticated users with Firewall: Rules or NAT: Port Forward privileges to inject scripts via the separator color field. Attackers can submit a crafted separator[] color value that displayseparator() renders unencoded into class attributes, executing in administrators' browsers to perform WebGUI actions with their privileges.

Netgate pfSense CE through 2.9.0 contains an OS command injection vulnerability that allows authenticated users with Virtual IP edit privileges to execute commands as root by storing an unvalidated CARP VHID. Attackers can supply a VHID containing shell metacharacters that executes via interfaceipaliasconfigure() ifconfig calls or getcarpinterfacestatus() when CARP status is rendered.

Netgate pfSense CE 2.7.0 through 2.9.0 contains an OS command injection vulnerability that allows authenticated users with Traffic Shaper Limiters privileges to execute root commands by tampering with the limiter number field. Attackers can submit a malicious hidden 'number' value when editing a limiter, then delete it so deletequeue() passes the unquoted value to dnctl via /bin/sh as root.

Netgate pfSense CE through 2.9.0 contains a newline injection vulnerability in servicespppoeedit.php that allows privileged users to inject mpd.secret entries via unvalidated username POST fields. Attackers with the PPPoE Server Edit privilege can add a line whose secret begins with '!', making mpd5 run commands as root when a PPPoE client authenticates.

Netgate pfSense CE 2.7.0 through 2.9.0 contains an OS command injection vulnerability that allows authenticated users with QinQ edit privilege to run commands by storing an unvalidated parent interface name. Attackers can save a crafted 'if' value, then edit the QinQ entry so it is interpolated into ifconfig shell commands, executing commands as root.

Netgate pfSense CE through 2.9.0 contains an OS command injection vulnerability that allows authenticated users to execute commands as root by supplying a crafted wireless parent interface name. Attackers with limited Wireless Edit or Interface Assignments privileges can submit values like ath0;<cmd> via interfaceswirelessedit.php or interfacesassign.php, which interfacewirelessclone() interpolates unescaped into an ifconfig shell command.

Netgate pfSense CE 2.7.0 through 2.9.0 contains a configuration injection vulnerability that allows authenticated users with IPsec Mobile privileges to execute commands as root via the loginbanner field. Attackers can submit a single-line banner containing '}' to escape the unquoted strongswan.conf attr value and define charon.start-scripts entries that charon executes as root on restart.

Netgate pfSense CE 2.5.0 through 2.9.0 contains an OS command injection vulnerability in openvpn.learn-address.sh that allows authenticated VPN clients to execute commands as the unbound user. Attackers can embed shell metacharacters in the certificate common name or username, which is interpolated unquoted into su -c strings, when DNS Resolver client registration is enabled.

Netgate pfSense CE from 2.7.1 through 2.9.0 contains a CRLF injection vulnerability in servicesunboundadvanced.php that allows authenticated users with DNS Resolver: Advanced privilege to inject Unbound directives. Attackers can embed CR/LF characters in the unvalidated sockqueuetimeout parameter, which is written raw into unbound.conf, to override local records and forwarding for all clients.

Netgate pfSense CE through 2.9.0 contains a local file read vulnerability that allows users with the Dynamic DNS client privilege to read files as root by setting a file:// custom Update URL in servicesdyndnsedit.php. Attackers can set a non-matching Result Match string so checkStatus() logs file contents such as /conf/config.xml or /etc/master.passwd to the system log.

Netgate pfSense CE 2.7.1 through 2.9.0 contains a reflected cross-site scripting vulnerability in firewallrules.php that allows remote attackers to inject script via the unencoded if parameter. When the non-default Require Firewall Interface option is enabled, attackers can lure users with firewall rules privileges into opening a crafted GET link to execute script in the WebGUI with their privileges.

Netgate pfSense FRR package (pfSense-pkg-frr) 2.0.21 and source revision 2.1.21 contain an OS command injection vulnerability in the FRR status filter. An authenticated WebGUI user with only the page-status-frr privilege can supply a filter value that breaks out of a single-quoted sed expression into which escapeshellarg() output is concatenated. Shell command substitution is then evaluated by a popen() pipeline, allowing attacker-selected commands to execute as root. There are updated FRR packages for pfSense Plus 26.07/26.03.1 and CE 2.9.0/2.8.1.

pfSense CE through 2.9.0 contains an OS command injection vulnerability in the OpenVPN openvpn.connectasync.sh script that allows authenticated VPN users to execute commands as root via crafted usernames. Attackers authenticated through RADIUS or LDAP can use usernames containing single quotes and shell metacharacters to break out of the eval'd pfctl anchor name on connect or disconnect.

pfSense CE through 2.9.0 contains a crontab injection vulnerability in interfacespppsedit.php that allows authenticated users to execute commands as root by injecting newlines into the ptpid or reset hour/minute fields. Attackers holding the 'WebCfg - Interfaces: PPPs: Edit' privilege can submit crafted POST values that configurecron() writes unescaped into /etc/crontab, running arbitrary root commands on schedule.

Netgate pfSense CE Suricata Path Traversal Remote Code Execution Vulnerability. This vulnerability allows remote attackers to create arbitrary files on affected installations of Netgate pfSense. Authentication is required to exploit this vulnerability.

The specific flaw exists within the Suricata package. The issue results from the lack of proper validation of a user-supplied path prior to using it in file operations. An attacker can leverage this vulnerability to create files in the context of root. Was ZDI-CAN-28085.

pfSense Plus before 26.07 and CE before 2.9.0 allow authenticated users with the Firewall: Schedules: Edit privilege to inject arbitrary JavaScript via the descr parameter in /firewallscheduleedit.php. The schedule description is stored without HTML sanitization and subsequently inserted into an HTML attribute value in /firewallrules.php with only single-quote escaping applied, permitting double-quote breakout. The payload executes in the browser of any user with the Firewall: Rules privilege who views the rules list with the affected schedule attached.

pfSense Plus before 26.07 and CE before 2.9.0 allow authenticated users with the Status: Monitoring privilege to inject arbitrary JavaScript via graph configuration parameters in /statusmonitoring.php. Multiple POST parameters including graph-left, graph-right, time-period, resolution, start-date, end-date, start-time, end-time, graph-type, invert, and refresh-interval are concatenated and written to the global pfSense XML configuration without sanitization, then echoed unsanitized into a JavaScript string context on page render. Because the setting is stored in the global configuration, the payload executes in the browser of every user who visits the Status: Monitoring page.

pfSense Plus before 26.07 and pfSense CE through 2.8.1 contain a stored cross-site scripting vulnerability in the Traffic Graphs top-talkers feature, where PTR records returned by reverse DNS lookups are incorporated without sanitization into AJAX responses and rendered as HTML through a DOM sink in the administrator interface. An attacker who controls a PTR record and generates sufficient traffic to appear as a top talker can execute arbitrary JavaScript in an administrator's browser, gaining access to the authenticated session context and same-origin access to the firewall management interface, enabling account creation and arbitrary OS command execution.