Openssh

Memory corruption in the OpenSSH client (ssh) before 10.4 lets a malicious or compromised SSH server trigger a use-after-free on the connecting client by changing its host key during a key re-exchange (rekey), potentially leading to information disclosure or code execution in the client process. Only the client side is affected; the server is not vulnerable. There is no public exploit identified at time of analysis and it is not on CISA KEV, and EPSS is low (0.25%, 16th percentile), but the flaw is fixed in OpenSSH 10.4/10.4p1.

OpenSSH sshd before version 10.4 fails to consistently enforce its built-in minimum authentication delay, undermining the rate-limiting defense designed to slow credential-guessing attacks against SSH services. All OpenSSH releases prior to 10.4 are affected across all platforms, enabling unauthenticated remote attackers to submit authentication attempts at a rate higher than the daemon intends to permit. No public exploit code has been identified and the vulnerability is absent from CISA KEV; however, the trivial attack complexity combined with OpenSSH's near-universal deployment footprint makes prompt patching appropriate.

Denial of service in OpenSSH sshd before 10.4 lets remote unauthenticated attackers exhaust server resources by driving excessive authentication attempts, because the MaxAuthTries cap was not correctly enforced for the GSSAPIAuthentication path. Only deployments that have enabled GSSAPI-based authentication are exposed, and there is no public exploit identified at time of analysis. EPSS is low (0.34%, 26th percentile) and CISA SSVC records no observed exploitation, so this is a real but non-urgent availability issue rather than a code-execution threat.

Security-control bypass in OpenSSH sshd before 10.4 causes the DisableForwarding=yes hardening directive to be silently ignored when PermitTunnel=yes is also set, so tun-device forwarding remains available despite an administrator's explicit policy to disable all forwarding. Affected operators are those who rely on DisableForwarding as a defense-in-depth restriction; the flaw lets an authenticated user establish layer-2/3 tunnels the configuration was meant to forbid. There is no public exploit identified at time of analysis, EPSS is low (0.13%, 3rd percentile), and it is not on CISA KEV.

OpenSSH sshd before version 10.4 silently ignores the GSSAPIStrictAcceptorCheck configuration directive when the server is integrated with Windows Active Directory, defeating a security control that administrators rely on to enforce GSSAPI acceptor name validation during Kerberos-based SSH authentication. This undocumented behavior means AD-joined SSH servers may accept GSSAPI authentications against unintended Kerberos service principals regardless of how the option is configured, yielding limited confidentiality and integrity impact. No public exploits or active exploitation have been identified; the CVSS AC:H rating reflects the specific environmental prerequisites required for exploitation.

OpenSSH's internal-sftp subsystem silently discards all command-line arguments beyond position 9, allowing authenticated SFTP users to bypass security restrictions that administrators intended to enforce via those later-positioned arguments. All OpenSSH releases before 10.4 are affected when sshd_config supplies more than nine arguments to the internal-sftp subsystem, which is a non-default but legitimate administrative pattern used for directory restriction, read-only enforcement, and umask control. No public exploit has been identified and this vulnerability is not listed in the CISA KEV catalog; however, sites relying on complex internal-sftp argument chains for access policy enforcement face a direct, silent policy bypass.

Path traversal in the scp utility of OpenSSH before 10.4 causes files to be written into the parent directory of the intended destination during remote-to-remote copy operations. The root cause is CWE-23 (Relative Path Traversal): scp fails to canonicalize or sanitize paths when relaying data between two remote hosts, allowing an attacker controlling a malicious endpoint to influence where transferred files land. No public exploit identified at time of analysis, and active exploitation has not been confirmed by CISA KEV; the CVSS AC:H and UI:R metrics significantly constrain real-world exploitability.

Path traversal in the OpenSSH sftp client before version 10.4p1 allows an attacker-controlled server to write downloaded files outside the user's intended target directory when the 'sftp server:/path .' bulk-download syntax is used. Affected are all OpenSSH deployments where users sftp from untrusted or attacker-controlled hosts, which in practice spans virtually every Linux and Unix environment. No public exploit has been identified at time of analysis and the vulnerability is not listed in CISA KEV, though the ubiquity of OpenSSH elevates aggregate exposure despite the moderate per-instance severity.

OpenSSH before 10.3 fails to confirm connection multiplexing in proxy-mode sessions, allowing local attackers with user interaction to bypass intended access controls and potentially manipulate multiplexed connections. The vulnerability affects OpenSSH versions prior to 10.3p1 and requires local access with user interaction (UI:R) on the affected system; while the CVSS score is low (2.5) and integrity impact is limited, the omission of confirmation mechanisms in proxy-mode multiplexing creates a logic flaw that could enable unauthorized session hijacking or redirection in multi-user environments.

OpenSSH before 10.3 incorrectly interprets ECDSA algorithm specifications in PubkeyAcceptedAlgorithms and HostbasedAcceptedAlgorithms configuration options, allowing authenticated users to authenticate using unintended ECDSA variants. The vulnerability requires authenticated network access and high attack complexity, resulting in a low CVSS score of 3.1 with integrity impact but no confidentiality or availability loss. No public exploit code or active exploitation has been documented.

Argument/command injection in OpenSSH before 10.3 lets shell metacharacters embedded in an untrusted username trigger command execution on the SSH-client host. It affects deployments that both feed an attacker-influenced username to the ssh command line and use a non-default ssh_config where %-token expansion (e.g. in ProxyCommand/LocalCommand) is enabled. There is no public exploit identified at time of analysis, EPSS is negligible (0.01%), and it is not in CISA KEV; a fixed release (10.3/10.3p1) is available.

OpenSSH before version 10.3 mishandles the authorized_keys principals option when a principals list is combined with a Certificate Authority that uses certain comma character patterns, allowing authenticated local or remote users to disclose sensitive authorization information or manipulate authentication decisions. This vulnerability affects all OpenSSH versions prior to 10.3p1 and requires authenticated access (PR:L) with non-trivial attack complexity (AC:H), resulting in partial confidentiality and integrity impact. No public exploit code or active exploitation has been identified at time of analysis.

Privilege-escalation exposure in OpenSSH before 10.3 (fixed in 10.3p1) where scp, when run by root using the legacy SCP protocol flag -O and without -p (preserve mode), may write a downloaded file with setuid or setgid bits set, contrary to user expectation. A malicious or compromised SSH server (or a man-in-the-middle on the transfer) could thereby cause an attacker-controlled binary to land on disk as a setuid/setgid-root executable, enabling local privilege escalation when it is later run. There is no public exploit identified at time of analysis, EPSS is very low (0.04%), and CISA SSVC rates exploitation as 'none' though technical impact as 'total'.

Vulnerability in the OpenSSH GSSAPI delta included in various Linux distributions. This vulnerability affects the GSSAPI patches added by various Linux distributions and does not affect the OpenSSH upstream project itself.

In sshd in OpenSSH before 10.0, the DisableForwarding directive does not adhere to the documentation stating that it disables X11 and agent forwarding. Rated medium severity (CVSS 4.3), this vulnerability is no authentication required, low attack complexity.

A flaw was found in the OpenSSH package. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. Epss exploitation probability 42.5% and no vendor patch available.

A vulnerability was found in OpenSSH when the VerifyHostKeyDNS option is enabled. Rated medium severity (CVSS 6.8), this vulnerability is remotely exploitable, no authentication required. Epss exploitation probability 60.0%.

Remote code execution in OpenSSH's sshd server (regression of CVE-2006-5051) allows unauthenticated remote attackers to exploit a signal handler race condition by failing to authenticate within the LoginGraceTime window, potentially yielding root-level code execution on glibc-based Linux systems. The flaw - widely known as 'regreSSHion' - affects numerous distributions and vendor appliances including Ubuntu 23.10/24.04, AlmaLinux 9, SonicWall SMA firmware, Arista EOS, NetApp ONTAP, and others. Publicly available exploit code exists and EPSS scores it at 48.06% (98th percentile), reflecting very high exploitation likelihood, though it is not currently listed in CISA KEV.

OpenSSH through 10.0, when common types of DRAM are used, might allow row hammer attacks (for authentication bypass) because the integer value of authenticated in mm_answer_authpassword does not. Rated high severity (CVSS 7.0). No vendor patch available.

In ssh in OpenSSH before 9.6, OS command injection might occur if a user name or host name has shell metacharacters, and this name is referenced by an expansion token in certain situations. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and EPSS exploitation probability 16.5%.

In ssh-agent in OpenSSH before 9.6, certain destination constraints can be incompletely applied. Rated medium severity (CVSS 5.5), this vulnerability is low attack complexity.

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. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. Public exploit code available and EPSS exploitation probability 53.6%.

The PKCS#11 feature in ssh-agent in OpenSSH before 9.3p2 has an insufficiently trustworthy search path, leading to remote code execution if an agent is forwarded to an attacker-controlled system. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.

ssh-add in OpenSSH before 9.3 adds smartcard keys to ssh-agent without the intended per-hop destination constraints. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

OpenSSH server (sshd) 9.1 introduced a double-free vulnerability during options.kex_algorithms handling. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploitable, no authentication required. Public exploit code available and EPSS exploitation probability 88.3%.

An issue was discovered in OpenSSH before 8.9. Rated low severity (CVSS 3.7), this vulnerability is remotely exploitable, no authentication required. This Improper Authentication vulnerability could allow attackers to bypass authentication mechanisms to gain unauthorized access.

sshd in OpenSSH 6.2 through 8.x before 8.8, when certain non-default configurations are used, allows privilege escalation because supplemental groups are not initialized as expected. Rated high severity (CVSS 7.0).

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. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and EPSS exploitation probability 14.6%.

ssh-agent in OpenSSH before 8.5 has a double free that may be relevant in a few less-common scenarios, such as unconstrained agent-socket access on a legacy operating system, or the forwarding of an. Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable.

scp in OpenSSH through 8.3p1 allows command injection in the scp.c toremote function, as demonstrated by backtick characters in the destination argument. Rated high severity (CVSS 7.4), this vulnerability is low attack complexity. Public exploit code available and no vendor patch available.

The client side in OpenSSH 5.7 through 8.4 has an Observable Discrepancy leading to an information leak in the algorithm negotiation. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required.

The scp client in OpenSSH 8.2 incorrectly sends duplicate responses to the server upon a utimes system call failure, which allows a malicious unprivileged user on the remote server to overwrite. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.

OpenSSH 7.7 through 7.9 and 8.x before 8.1, when compiled with an experimental key type, has a pre-authentication integer overflow if a client or server is configured to use a crafted XMSS key. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. Public exploit code available.

An issue was discovered in OpenSSH 7.9. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. Public exploit code available.

In OpenSSH 7.9, due to accepting and displaying arbitrary stderr output from the server, a malicious server (or Man-in-The-Middle attacker) can manipulate the client output, for example to use ANSI. Rated medium severity (CVSS 6.8), this vulnerability is remotely exploitable, no authentication required. Public exploit code available.

An issue was discovered in OpenSSH 7.9. Rated medium severity (CVSS 6.8), this vulnerability is remotely exploitable, no authentication required.

Remotely observable behaviour in auth-gss2.c in OpenSSH through 7.8 could be used by remote attackers to detect existence of users on a target system when GSS2 is in use. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Exposure of Sensitive Information vulnerability could allow attackers to access sensitive data that should not be disclosed.

OpenSSH through 7.7 is prone to a user enumeration vulnerability due to not delaying bailout for an invalid authenticating user until after the packet containing the request has been fully parsed,. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.

sshd in OpenSSH before 7.4 allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via an out-of-sequence NEWKEYS message, as demonstrated by Honggfuzz,. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity.

The auth_password function in auth-passwd.c in sshd in OpenSSH before 7.3 does not limit password lengths for password authentication, which allows remote attackers to cause a denial of service. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and EPSS exploitation probability 75.8%.

The do_setup_env function in session.c in sshd in OpenSSH through 7.2p2, when the UseLogin feature is enabled and PAM is configured to read .pam_environment files in user home directories, allows. Rated high severity (CVSS 7.8), this vulnerability is low attack complexity. No vendor patch available.

The ssh_packet_read_poll2 function in packet.c in OpenSSH before 7.1p2 allows remote attackers to cause a denial of service (out-of-bounds read and application crash) via crafted network traffic. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.

sshd in OpenSSH 6.8 and 6.9 uses world-writable permissions for TTY devices, which allows local users to cause a denial of service (terminal disruption) or possibly have unspecified other impact by. Rated high severity (CVSS 7.2), this vulnerability is low attack complexity. Public exploit code available and no vendor patch available.

The x11_open_helper function in channels.c in ssh in OpenSSH before 6.9, when ForwardX11Trusted mode is not used, lacks a check of the refusal deadline for X connections, which makes it easier for. Rated medium severity (CVSS 4.3), this vulnerability is remotely exploitable. No vendor patch available.

The OpenSSH server, as used in Fedora and Red Hat Enterprise Linux 7 and when running in a Kerberos environment, allows remote authenticated users to log in as another user when they are listed in. Rated medium severity (CVSS 4.0), this vulnerability is remotely exploitable, low attack complexity. No vendor patch available.

The mm_newkeys_from_blob function in monitor_wrap.c in sshd in OpenSSH 6.2 and 6.3, when an AES-GCM cipher is used, does not properly initialize memory for a MAC context data structure, which allows. Rated medium severity (CVSS 6.0), this vulnerability is remotely exploitable. No vendor patch available.

The auth_parse_options function in auth-options.c in sshd in OpenSSH before 5.7 provides debug messages containing authorized_keys command options, which allows remote authenticated users to obtain. Rated low severity (CVSS 3.5), this vulnerability is remotely exploitable. No vendor patch available.