CVE-2026-59998

sshd in OpenSSH before 10.4 has an undocumented security-relevant behavior: GSSAPIStrictAcceptorCheck has no value if the server is in Windows Active Directory.

sshd in OpenSSH before 10.4 has an undocumented security-relevant behavior: GSSAPIStrictAcceptorCheck has no value if the server is in Windows Active Directory.

sshd in OpenSSH before 10.4 has an undocumented security-relevant behavior: GSSAPIStrictAcceptorCheck has no value if the server is in Windows Active Directory.

OpenSSH is an SSH protocol implementation supported by a number of Linux, UNIX, and similar operating systems. It includes the core files necessary for both the OpenSSH client and server.

Security Fix(es):

• openssh: OpenSSH: SFTP security bypass due to command-line argument parsing flaw (CVE-2026-59997)

• openssh: OpenSSH: Undocumented GSSAPIStrictAcceptorCheck behavior impacts security in Windows Active Directory (CVE-2026-59998)

• openssh: OpenSSH: Denial of Service via excessive GSSAPI authentication attempts (CVE-2026-60000)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

OpenSSH is an SSH protocol implementation supported by a number of Linux, UNIX, and similar operating systems. It includes the core files necessary for both the OpenSSH client and server.

Security Fix(es):

• openssh: OpenSSH: SFTP security bypass due to command-line argument parsing flaw (CVE-2026-59997)

• openssh: OpenSSH: Undocumented GSSAPIStrictAcceptorCheck behavior impacts security in Windows Active Directory (CVE-2026-59998)

• openssh: OpenSSH: Denial of Service via excessive GSSAPI authentication attempts (CVE-2026-60000)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

OpenSSH is an SSH protocol implementation supported by a number of Linux, UNIX, and similar operating systems. It includes the core files necessary for both the OpenSSH client and server.

Security Fix(es):

• openssh: OpenSSH: SFTP security bypass due to command-line argument parsing flaw (CVE-2026-59997)

• openssh: OpenSSH: Undocumented GSSAPIStrictAcceptorCheck behavior impacts security in Windows Active Directory (CVE-2026-59998)

• openssh: OpenSSH: Brute-force attacks facilitated due to insufficient authentication delay (CVE-2026-60001)

• openssh: OpenSSH: Denial of Service via excessive GSSAPI authentication attempts (CVE-2026-60000)

• openssh: OpenSSH: Tunnel forwarding restriction bypass (CVE-2026-73283)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

sshd in OpenSSH before 10.4 has an undocumented security-relevant behavior: GSSAPIStrictAcceptorCheck has no value if the server is in Windows Active Directory.

OpenSSH is an SSH protocol implementation supported by a number of Linux, UNIX, and similar operating systems. It includes the core files necessary for both the OpenSSH client and server.

Security Fix(es):

• openssh: OpenSSH: SFTP security bypass due to command-line argument parsing flaw (CVE-2026-59997)
• openssh: OpenSSH: Undocumented GSSAPIStrictAcceptorCheck behavior impacts security in Windows Active Directory (CVE-2026-59998)
• openssh: OpenSSH: Denial of Service via excessive GSSAPI authentication attempts (CVE-2026-60000)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

OpenSSH is an SSH protocol implementation supported by a number of Linux, UNIX, and similar operating systems. It includes the core files necessary for both the OpenSSH client and server.

Security Fix(es):

• openssh: OpenSSH: SFTP security bypass due to command-line argument parsing flaw (CVE-2026-59997)
• openssh: OpenSSH: Undocumented GSSAPIStrictAcceptorCheck behavior impacts security in Windows Active Directory (CVE-2026-59998)
• openssh: OpenSSH: Denial of Service via excessive GSSAPI authentication attempts (CVE-2026-60000)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

OpenSSH is an SSH protocol implementation supported by a number of Linux, UNIX, and similar operating systems. It includes the core files necessary for both the OpenSSH client and server.

Security Fix(es):

• openssh: OpenSSH: SFTP security bypass due to command-line argument parsing flaw (CVE-2026-59997)
• openssh: OpenSSH: Undocumented GSSAPIStrictAcceptorCheck behavior impacts security in Windows Active Directory (CVE-2026-59998)
• openssh: OpenSSH: Brute-force attacks facilitated due to insufficient authentication delay (CVE-2026-60001)
• openssh: OpenSSH: Denial of Service via excessive GSSAPI authentication attempts (CVE-2026-60000)
• openssh: OpenSSH: Tunnel forwarding restriction bypass (CVE-2026-73283)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

sshd in OpenSSH before 10.4 has an undocumented security-relevant behavior: GSSAPIStrictAcceptorCheck has no value if the server is in Windows Active Directory.

• CVE-2026-59998: document that GSSAPIStrictAcceptorCheck is ineffective when the server is joined to a Windows Active Directory. Backport upstream commit 8058c5bd.

• CVE-2026-59998: document that GSSAPIStrictAcceptorCheck is ineffective when the server is joined to a Windows Active Directory. Backport upstream commit 8058c5bd.

Local mitm of x11 forwarding via abstract unix socket pre-binding in Red Hat Enterprise Linux openssh client versions. (CVE-2026-55655) sftp in OpenSSH before 10.4 does not properly constrain the location of downloaded files when "sftp server:/path ." is used with an attacker-controlled server. (CVE-2026-59995) scp in OpenSSH before 10.4 may place a file in the parent directory of an intended directory when the copy occurs between two remote destinations. (CVE-2026-59996) internal-sftp in sshd in OpenSSH before 10.4 recognizes only the first 9 command-line arguments, which can be important if a later command-line argument would have helped to ensure the intended security properties of an SFTP connection. (CVE-2026-59997) sshd in OpenSSH before 10.4 has an undocumented security-relevant behavior: GSSAPIStrictAcceptorCheck has no value if the server is in Windows Active Directory. (CVE-2026-59998) In sshd in OpenSSH before 10.4, DisableForwarding=yes was supposed to take precedence over PermitTunnel=yes, but did not. (CVE-2026-59999) sshd in OpenSSH before 10.4 allows remote attackers to cause a denial of service (resource consumption from excessive authentication attempts) because MaxAuthTries was mishandled for GSSAPIAuthentication. (CVE-2026-60000) sshd in OpenSSH before 10.4 does not always honor the minimum authentication delay. (CVE-2026-60001) ssh in OpenSSH before 10.4 can have a use-after-free when a server changes its host key during a key re-exchange. (This outcome occurs only on the client side.). (CVE-2026-60002) In ssh-agent in OpenSSH before 10.5, some operations can occur remotely but were intended to occur only locally, including operations that add tokens or use keys. This is caused by misinteraction between agent locking and the [email protected] extension. (CVE-2026-73281) In ssh in OpenSSH before 10.5, a use-after-free for realloc data can occur if a certain pair of remote-forwarding operations are concurrent. (CVE-2026-73282) In sshd in OpenSSH before 10.5, the restrict keyword (in authorized_keys) was supposed to be applicable to tunnel forwarding but was not. (CVE-2026-73283) In sftp in OpenSSH before 10.6, a server can trigger directory traversal (causing files to be written to unintended locations) during a recursive copy operation. (CVE-2026-106552) In sshd in OpenSSH before 10.6, credentials can incorrectly persist after failure of a GSSAPIAuthentication authentication attempt. (CVE-2026-106553) In sshd in OpenSSH before 10.6, GSSAPIAuthentication authentication state can incorrectly be persisted across authentication attempts. (CVE-2026-106555) In sshd and ssh in OpenSSH before 10.6, an LZ77 dictionary coder can be used even though this is contraindicated by the arXiv 2609.07709 "Crossing the Streams" findings. (CVE-2026-106582) In ssh in OpenSSH before 10.6, a $ or \ character can occur in a command-line username, leading to injection. (CVE-2026-106583) In ssh-keygen in OpenSSH before 10.6, certificates could have incorrect expiration times because of Daylight Saving mishandling. There can be a slightly more severe effect on users in certain Antarctic locations. (CVE-2026-106584) In sshd and ssh in OpenSSH before 10.6, there is no check for whether the maximum packet length is exceeded during decompression of highly compressed data. (CVE-2026-106585) In sshd in OpenSSH before 10.6, the restrict keyword (in authorized_keys) was supposed to be applicable to tunnel forwarding but was not, a different vulnerability than CVE-2026-73283. (CVE-2026-106586) In sshd in OpenSSH before 10.6, the value "none" for a configuration option is sometimes interpreted as a filename but was intended to mean that a feature is disabled. (CVE-2026-106587)

This update for openssh fixes the following issues:

• CVE-2026-59995: sftp: location of downloaded files not properly constrained when sftp server:/path . is used with an attacker-controlled server (bsc#1271044).
• CVE-2026-59996: scp: file placed in the parent directory of an intended target directory when copy occurs between two remote destinations (bsc#1271046).
• CVE-2026-59997: sshd: internal-sftp command lines are silently truncated after the 9th argument (bsc#1271048).
• CVE-2026-59998: sshd: undocumented security-relevant GSSAPIStrictAcceptorCheck behavior in Windows Active Directory is not documented (bsc#1271049).
• CVE-2026-59999: sshd: DisableForwarding=yes does not override PermitTunnel=yes (bsc#1271052).
• CVE-2026-60000: sshd: pre-authentication denial of service when GSSAPIAuthentication is enabled (bsc#1271053).
• CVE-2026-60001: sshd: minimum authentication delay is not honored (bsc#1271054).
• CVE-2026-60002: ssh: client-side use-after-free when a server changes its host key during a key reexchange (bsc#1271055).

Root has patched CVE-2026-59998 in the openssh package for Root:Debian:11. Multiple fixed versions available.

Root has patched CVE-2026-59998 in the openssh package for Root:Debian:12. Multiple fixed versions available.

Root has patched CVE-2026-59998 in the openssh package for Root:Debian:13. Multiple fixed versions available.

This update for openssh fixes the following issues:

• CVE-2026-59995: sftp: location of downloaded files not properly constrained when sftp server:/path . is used with an attacker-controlled server (bsc#1271044).
• CVE-2026-59996: scp: file placed in the parent directory of an intended target directory when copy occurs between two remote destinations (bsc#1271046).
• CVE-2026-59997: sshd: internal-sftp command lines are silently truncated after the 9th argument (bsc#1271048).
• CVE-2026-59998: sshd: undocumented security-relevant GSSAPIStrictAcceptorCheck behavior in Windows Active Directory is not documented (bsc#1271049).
• CVE-2026-59999: sshd: DisableForwarding=yes does not override PermitTunnel=yes (bsc#1271052).
• CVE-2026-60000: sshd: pre-authentication denial of service when GSSAPIAuthentication is enabled (bsc#1271053).
• CVE-2026-60001: sshd: minimum authentication delay is not honored (bsc#1271054).
• CVE-2026-60002: ssh: client-side use-after-free when a server changes its host key during a key reexchange (bsc#1271055).

This update for openssh fixes the following issues:

• CVE-2026-59995: sftp: a malicious server could change the the location of downloaded files (bsc#1271044).
• CVE-2026-59996: scp: a malicious server could write files to the parent directory of the intended target directory (bsc#1271046).
• CVE-2026-59997: sshd: internal-sftp command lines are silently truncated after the 9th argument (bsc#1271048).
• CVE-2026-59998: sshd: Undocumented GSSAPIStrictAcceptorCheck behavior impacts security in Windows Active Directory (bsc#1271049).
• CVE-2026-59999: sshd: DisableForwarding=yes didn't override PermitTunnel=yes (bsc#1271052).
• CVE-2026-60000: sshd: pre-authentication denial of service when GSSAPIAuthentication is enabled (bsc#1271053).
• CVE-2026-60001: sshd: honor the minimum authentication delay (bsc#1271054).
• CVE-2026-60002: ssh: client-side use-after-free when a server changes its host key during a key reexchange (bsc#1271055).
• CVE-2026-73281: refused binding requests on locked SSH agents can allow destination restriction bypasses (bsc#1275075).
• CVE-2026-73282: unsynchronized remote forwarding updates in SSH client multiplexing can cause use-after-free (bsc#1275074).
• CVE-2026-73283: unenforced restriction keywords on tunnel forwarding can allow administrative security policy bypasses (bsc#1275079).

This update for openssh fixes the following issues:

• CVE-2026-59995: sftp: a malicious server could change the the location of downloaded files (bsc#1271044).
• CVE-2026-59996: scp: a malicious server could write files to the parent directory of the intended target directory (bsc#1271046).
• CVE-2026-59997: sshd: internal-sftp command lines are silently truncated after the 9th argument (bsc#1271048).
• CVE-2026-59998: sshd: Undocumented GSSAPIStrictAcceptorCheck behavior impacts security in Windows Active Directory (bsc#1271049).
• CVE-2026-59999: sshd: DisableForwarding=yes didn't override PermitTunnel=yes (bsc#1271052).
• CVE-2026-60000: sshd: pre-authentication denial of service when GSSAPIAuthentication is enabled (bsc#1271053).
• CVE-2026-60001: sshd: honor the minimum authentication delay (bsc#1271054).
• CVE-2026-60002: ssh: client-side use-after-free when a server changes its host key during a key reexchange (bsc#1271055).

This update for openssh fixes the following issues:

• Backported support for the mlkemx25519 key exchange from upstream (jsc#PED-16473).

• CVE-2026-59995: sftp: location of downloaded files not properly constrained when sftp server:/path . is used with an attacker-controlled server (bsc#1271044).

• CVE-2026-59996: scp: file placed in the parent directory of an intended target directory when copy occurs between two remote destinations (bsc#1271046).

• CVE-2026-59997: sshd: internal-sftp command lines are silently truncated after the 9th argument (bsc#1271048).

• CVE-2026-59998: sshd: undocumented security-relevant GSSAPIStrictAcceptorCheck behavior in Windows Active Directory is not documented (bsc#1271049).

• CVE-2026-59999: sshd: DisableForwarding=yes does not override PermitTunnel=yes (bsc#1271052).

• CVE-2026-60000: sshd: pre-authentication denial of service when GSSAPIAuthentication is enabled (bsc#1271053).

• CVE-2026-60001: sshd: minimum authentication delay is not honored (bsc#1271054).

• CVE-2026-60002: ssh: client-side use-after-free when a server changes its host key during a key reexchange (bsc#1271055).

This update for openssh8.4 fixes the following issues:

• CVE-2026-59995: sftp: a malicious server could change the the location of downloaded files (bsc#1271044).
• CVE-2026-59997: sshd: internal-sftp command lines are silently truncated after the 9th argument (bsc#1271048).
• CVE-2026-59998: sshd: Undocumented GSSAPIStrictAcceptorCheck behavior impacts security in Windows Active Directory (bsc#1271049).
• CVE-2026-59999: sshd: DisableForwarding=yes didn't override PermitTunnel=yes (bsc#1271052).
• CVE-2026-60000: sshd: pre-authentication denial of service when GSSAPIAuthentication is enabled (bsc#1271053).
• CVE-2026-60001: sshd: honor the minimum authentication delay (bsc#1271054).
• CVE-2026-60002: ssh: client-side use-after-free when a server changes its host key during a key reexchange (bsc#1271055).

It was discovered that OpenSSH sftp did not properly constrain the location of downloaded files when connecting to an attacker-controlled server. An attacker could possibly use this issue to write files to unintended locations on the file system. (CVE-2026-59995)

It was discovered that OpenSSH scp could place files in the parent directory of the intended destination when copying between two remote hosts. An attacker could possibly use this issue to write files to unintended locations. (CVE-2026-59996)

It was discovered that OpenSSH internal-sftp only recognized the first nine command-line arguments, This could result in certain security-sensitive arguments being ignored, contrary to expectations. (CVE-2026-59997)

It was discovered that OpenSSH had undocumented behaviour regarding the GSSAPIStrictAcceptorCheck option in environments using Windows Active Directory. The documentation has been updated to clarify use of the option. (CVE-2026-59998)

It was discovered that OpenSSH did not properly enforce precedence of DisableForwarding=yes over PermitTunnel=yes in server configurations. This could possibly result in intended network forwarding restrictions being bypassed, contrary to expectations. (CVE-2026-59999)

It was discovered that OpenSSH mishandled the MaxAuthTries limit for GSSAPI authentication. A remote attacker could use this issue to perform excessive authentication attempts. (CVE-2026-60000)

It was discovered that OpenSSH did not always honour the minimum authentication delay. An attacker could possibly use this issue to perform brute-force attacks more efficiently. (CVE-2026-60001)

It was discovered that the OpenSSH client had a use-after-free vulnerability when a server changed its host key during a key re-exchange. An attacker able to intercept communications could possibly use this issue to execute arbitrary code or obtain sensitive information. (CVE-2026-60002)

Florian Kohnhäuser discovered that OpenSSH incorrectly handled shell metacharacters in certain usernames. An attacker could possibly use this issue to execute arbitrary commands when certain non-default configurations were used, resulting in arbitrary code execution. This issue only affected Ubuntu 14.04 LTS. (CVE-2026-35386)

Christos Papakonstantinou discovered that OpenSSH incorrectly handled ECDSA algorithm restrictions. An attacker could possibly use this issue to cause unintended ECDSA algorithms to be accepted, resulting in security restrictions being bypassed. (CVE-2026-35387)

Vladimir Tokarev discovered that OpenSSH incorrectly handled certain principal restrictions in authorized_keys files. An attacker could possibly use this issue to bypass principal restrictions, resulting in unauthorized access. This issue only affected Ubuntu 14.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS. (CVE-2026-35414)

It was discovered that OpenSSH incorrectly handled downloaded file paths when using sftp with an untrusted server. An attacker could possibly use this issue to write downloaded files outside the intended location, resulting in unauthorized file modification. (CVE-2026-59995)

It was discovered that OpenSSH incorrectly handled command-line arguments in internal-sftp. An attacker could possibly use this issue to cause certain security-related arguments to be ignored, resulting in security restrictions being bypassed. (CVE-2026-59997)

It was discovered that OpenSSH incorrectly handled GSSAPIStrictAcceptorCheck when used with Windows Active Directory. An attacker could possibly use this issue to bypass GSSAPI security restrictions, resulting in unauthorized access. (CVE-2026-59998)

It was discovered that OpenSSH incorrectly handled forwarding restrictions when DisableForwarding and PermitTunnel were used together. An attacker could possibly use this issue to create tunnels despite forwarding being disabled, resulting in security restrictions being bypassed. This issue only affected Ubuntu 18.04 LTS and Ubuntu 20.04 LTS. (CVE-2026-59999)

It was discovered that OpenSSH incorrectly handled authentication attempt limits when using GSSAPI authentication. An attacker could possibly use this issue to consume excessive system resources, resulting in a denial of service. (CVE-2026-60000)

It was discovered that OpenSSH did not always enforce the minimum authentication delay. An attacker could possibly use this issue to perform authentication attempts more rapidly than intended, resulting in weakened brute-force protections. This issue only affected Ubuntu 20.04 LTS. (CVE-2026-60001)

It was discovered that OpenSSH incorrectly handled certain concurrent remote forwarding operations. An attacker could possibly use this issue to trigger a use-after-free, resulting in a denial of service or arbitrary code execution. (CVE-2026-73282)