CVE-2026-106555

In sshd in OpenSSH before 10.6, GSSAPIAuthentication authentication state can incorrectly be persisted across authentication attempts.

In sshd in OpenSSH before 10.6, GSSAPIAuthentication authentication state can incorrectly be persisted across authentication attempts.

In sshd in OpenSSH before 10.6, GSSAPIAuthentication authentication state can incorrectly be persisted across authentication attempts.

• CVE-2026-106555: reset GSSAPI client state before each authentication attempt
• CVE-2026-106553: store GSSAPI delegated credentials only after successful GSSAPI authentication
• CVE-2026-106583: disallow '$' and '' in command-line user names
• CVE-2026-106585: reject compressed packets that inflate beyond the maximum packet size

• CVE-2026-106555: reset GSSAPI client state before each authentication attempt
• CVE-2026-106553: store GSSAPI delegated credentials only after successful GSSAPI authentication
• CVE-2026-106583: disallow '$' and '' in command-line user names
• CVE-2026-106585: reject compressed packets that inflate beyond the maximum packet size

• CVE-2026-106555: reset GSSAPI client state before each authentication attempt (upstream 670510d1)
• CVE-2026-106553: store delegated GSSAPI credentials only after successful authorization (upstream 6f9cd19a)
• CVE-2026-106583: disallow '$' and '' in a command-line user name (upstream 0c4c9a7b)
• CVE-2026-106585: reject decompressed packets exceeding the maximum packet size (upstream e0f85d83)

• CVE-2026-106555: reset GSSAPI client state before each authentication attempt (upstream 670510d1)
• CVE-2026-106553: store delegated GSSAPI credentials only after successful authorization (upstream 6f9cd19a)
• CVE-2026-106583: disallow '$' and '' in a command-line user name (upstream 0c4c9a7b)
• CVE-2026-106585: reject decompressed packets exceeding the maximum packet size (upstream e0f85d83)

• SECURITY UPDATE: GSSAPI client state persisting across authentication attempts
  • debian/patches/CVE-2026-106555.patch: reset the GSSAPI client state at the start of each userauth request and of each pre-authentication GSSAPI context setup in the monitor.
  • CVE-2026-106555
• SECURITY UPDATE: GSSAPI delegated credentials stored after failed authentication
  • debian/patches/CVE-2026-106553.patch: only store delegated GSSAPI credentials when the GSSAPI client was authorized.
  • CVE-2026-106553
• SECURITY UPDATE: command injection via command-line user name
  • debian/patches/CVE-2026-106583.patch: disallow '$' and '' in a user name supplied on the ssh command line.
  • CVE-2026-106583

• CVE-2026-106555: reset GSSAPI client state before each authentication attempt (upstream 670510d1)
• CVE-2026-106553: store delegated GSSAPI credentials only after successful authorization (upstream 6f9cd19a)
• CVE-2026-106583: disallow '$' and '' in a command-line user name (upstream 0c4c9a7b)
• CVE-2026-106585: reject decompressed packets exceeding the maximum packet size (upstream e0f85d83)

• CVE-2026-106555: sshd kept GSSAPI client state from a partially completed GSSAPIAuthentication attempt and could reuse it in a later attempt; reset the global GSSAPI client state before each authentication attempt. Backport upstream commit 670510d1.
• CVE-2026-106553: sshd could store delegated GSSAPI credentials from a failed GSSAPIAuthentication attempt; only store them when GSSAPI user authorization succeeded. Backport upstream commit 6f9cd19a.
• CVE-2026-106583: ssh(1) accepted '$' and '\' in a command-line user name, allowing shell injection via expanded commands; reject both characters. Backport upstream commit 0c4c9a7b.
• CVE-2026-106585: ssh(1) and sshd did not check that decompressed packet payloads stay below the maximum packet size; reject oversized inflated payloads. Backport upstream commit e0f85d83.

• SECURITY UPDATE: GSSAPI client state and credentials persisted across authentication attempts
  • debian/patches/CVE-2026-106553-CVE-2026-106555.patch: add ssh_gssapi_cleanup_global_client() and call it before each userauth request in auth2.c and before each pre-auth GSSAPI context setup in monitor.c, and add a userok flag to ssh_gssapi_client so that ssh_gssapi_storecreds() only stores delegated credentials after successful authorization, in gss-serv.c and ssh-gss.h
  • CVE-2026-106553
  • CVE-2026-106555
• SECURITY UPDATE: Command injection via command-line username
  • debian/patches/CVE-2026-106583.patch: reject '$' and '' anywhere in a command-line supplied user name in valid_ruser(), in ssh.c
  • CVE-2026-106583
• SECURITY UPDATE: Decompression bomb exceeding maximum packet size
  • debian/patches/CVE-2026-106585.patch: fail uncompress_buffer() once the decompressed output reaches PACKET_MAX_SIZE, in packet.c
  • CVE-2026-106585

• CVE-2026-106555: sshd kept GSSAPI client state from a partially completed authentication attempt and could reuse it in a later attempt; reset it before each attempt. Backport upstream commits 670510d1 and d549f99d.
• CVE-2026-106553: sshd stored delegated GSSAPI credentials even when GSSAPI user authorization had not succeeded; store them only after it succeeds. Backport upstream commit 6f9cd19a.
• CVE-2026-106583: ssh(1) accepted '$' and '' in a command-line user name, allowing injection via shell-expanded commands; reject both characters. Backport upstream commit 0c4c9a7b.
• CVE-2026-106585: a compressed packet could inflate far beyond the maximum packet size and exhaust memory; reject it once the decompressed payload reaches PACKET_MAX_SIZE. Backport upstream commit e0f85d83.

• CVE-2026-106555: sshd kept GSSAPI client state from a partially completed authentication attempt and could reuse it in a later attempt; reset it before each attempt. Backport upstream commits 670510d1 and d549f99d.
• CVE-2026-106553: sshd stored delegated GSSAPI credentials even when GSSAPI user authorization had not succeeded; store them only after it succeeds. Backport upstream commit 6f9cd19a.
• CVE-2026-106583: ssh(1) accepted '$' and '' in a command-line user name, allowing injection via shell-expanded commands; reject both characters. Backport upstream commit 0c4c9a7b.
• CVE-2026-106585: a compressed packet could inflate far beyond the maximum packet size and exhaust memory; reject it once the decompressed payload reaches PACKET_MAX_SIZE. Backport upstream commit e0f85d83.

• CVE-2026-106555: sshd kept GSSAPI client state from a partially completed authentication attempt and could reuse it in a later attempt; reset it before each attempt. Backport upstream commits 670510d1 and d549f99d.
• CVE-2026-106553: sshd stored delegated GSSAPI credentials even when GSSAPI user authorization had not succeeded; store them only after it succeeds. Backport upstream commit 6f9cd19a.
• CVE-2026-106583: ssh(1) accepted '$' and '' in a command-line user name, allowing injection via shell-expanded commands; reject both characters. Backport upstream commit 0c4c9a7b.
• CVE-2026-106585: a compressed packet could inflate far beyond the maximum packet size and exhaust memory; reject it once the decompressed payload reaches PACKET_MAX_SIZE. Backport upstream commit e0f85d83.

• CVE-2026-106585: a compressed packet could inflate far beyond the maximum packet size and exhaust memory; reject it once the decompressed payload reaches PACKET_MAX_SIZE. Backport upstream commit e0f85d83.
• CVE-2026-106555: sshd kept GSSAPI client state from a partially completed authentication attempt and could reuse it in a later attempt; reset it before each attempt. Backport upstream commits 670510d1 and d549f99d.
• CVE-2026-106553: sshd stored delegated GSSAPI credentials even when GSSAPI user authorization had not succeeded; store them only after it succeeds. Backport upstream commit 6f9cd19a.
• CVE-2026-106583: ssh(1) accepted '$' and '' in a command-line user name, allowing injection via shell-expanded commands; reject both characters. Backport upstream commit 0c4c9a7b.

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)

Root has patched CVE-2026-106555 in the openssh package for Root:Debian:12. Multiple fixed versions available.

Root has patched CVE-2026-106555 in the openssh package for Root:Debian:13. Multiple fixed versions available.

It was discovered that OpenSSH's sftp client incorrectly handled paths returned by the server during a recursive copy operation. A remote attacker controlling the server could possibly use this issue to write files to unintended locations. (CVE-2026-106552)

It was discovered that OpenSSH's sshd server incorrectly handled GSSAPIAuthentication state across authentication attempts. An attacker could possibly use this issue to obtain credentials from a previous failed authentication attempt. (CVE-2026-106553, CVE-2026-106555)

It was discovered that OpenSSH incorrectly used an LZ77 dictionary coder during compression. An attacker could possibly use this issue to obtain sensitive information. (CVE-2026-106582)

It was discovered that OpenSSH's ssh client incorrectly allowed special characters in command-line usernames. An attacker could possibly use this issue to inject arbitrary commands via specially crafted usernames. (CVE-2026-106583)

It was discovered that OpenSSH's ssh-keygen incorrectly handled Daylight Saving Time when converting dates. An attacker could possibly use this issue to cause certificates to have incorrect expiration times. (CVE-2026-106584)

It was discovered that OpenSSH did not check whether the maximum packet length was exceeded during decompression. A remote attacker could possibly use this issue to cause a denial of service. (CVE-2026-106585)

It was discovered that OpenSSH's sshd server incorrectly applied the restrict keyword from authorized_keys to tunnel forwarding requests. A local attacker with an authorized key could possibly use this issue to bypass intended tunnel forwarding restrictions. (CVE-2026-106586)

It was discovered that OpenSSH's sshd server incorrectly handled certain configuration options that accept a "none" value. An attacker could possibly use this issue to cause OpenSSH to behave unexpectedly. (CVE-2026-106587)

It was discovered that OpenSSH's sftp client incorrectly handled paths returned by the server during a recursive copy operation. A remote attacker controlling the server could possibly use this issue to write files to unintended locations. (CVE-2026-106552)

It was discovered that OpenSSH's sshd server incorrectly handled GSSAPIAuthentication state across authentication attempts. An attacker could possibly use this issue to obtain credentials from a previous failed authentication attempt. (CVE-2026-106553, CVE-2026-106555)

It was discovered that OpenSSH incorrectly used an LZ77 dictionary coder during compression. An attacker could possibly use this issue to obtain sensitive information. (CVE-2026-106582)

It was discovered that OpenSSH's ssh client incorrectly allowed special characters in command-line usernames. An attacker could possibly use this issue to inject arbitrary commands via specially crafted usernames. (CVE-2026-106583)

It was discovered that OpenSSH's ssh-keygen incorrectly handled Daylight Saving Time when converting dates. An attacker could possibly use this issue to cause certificates to have incorrect expiration times. (CVE-2026-106584)

It was discovered that OpenSSH did not check whether the maximum packet length was exceeded during decompression. A remote attacker could possibly use this issue to cause a denial of service. (CVE-2026-106585)

It was discovered that OpenSSH's sshd server incorrectly applied the restrict keyword from authorized_keys to tunnel forwarding requests. A local attacker with an authorized key could possibly use this issue to bypass intended tunnel forwarding restrictions. (CVE-2026-106586)

It was discovered that OpenSSH's sshd server incorrectly handled certain configuration options that accept a "none" value. An attacker could possibly use this issue to cause OpenSSH to behave unexpectedly. (CVE-2026-106587)