Sicherheitslücken in snapd

Source-address critical option not enforced for non-public-key auth callbacks in golang.org/x/crypto/ssh

The source-address critical option in the Permissions returned by an authentication callback was only enforced for the PublicKeyCallback and VerifiedPublicKeyCallback paths, extending the fix for CVE-2026-46595. Permissions returned by the PasswordCallback, KeyboardInteractiveCallback, NoClientAuthCallback, and GSSAPIWithMICConfig.AllowLogin callbacks were not validated against the client's remote address, so a source-address restriction set by those callbacks was silently ignored. The check is now applied to the Permissions returned by any authentication callback.

snap-confine Local Privilege Escalation via Capabilities Misconfiguration or Flaw in Execution Environment Setup

A local privilege escalation vulnerability exists in snap-confine, a set-capabilities core component used internally by Canonical snapd to construct the secure execution environment for snap applications. This vulnerability uniquely affects versions of snap-confine configured with set-capabilities (rather than standard set-uid-root installations). Due to a flaw in how privilege boundaries or security sandboxes are initialized when the binary runs under limited ambient capabilities, a local, unprivileged attacker can exploit this behavior to bypass intended restrictions and execute arbitrary code. Successful exploitation allows the local user

• Auf 2.76+ubuntu24.04.1 aktualisieren

snapd snap-confine Sandbox Confinement Bypass via Omission of setuid Restriction in Seccomp Templates

A sandbox confinement bypass vulnerability exists in Canonical snapd within its internal execution environment compiler (snap-confine). The default seccomp security templates generated by the engine to restrict system calls do not filter or reject process operations capable of creating or manipulating file execution flags with set-user-ID attributes. Consequently, an application running within a strictly confined snap environment can successfully compile or drop binaries and apply setuid properties to them. If a compromised or malicious process inside the snap sandbox executes these generated setuid binaries, it can potentially circumvent ar

• Auf 2.76+ubuntu24.04.1 aktualisieren

AppArmor Base Profile Misconfiguration in snapd Permits Confined Snaps Unauthorized Access to Hashed Passwords via systemd-userdbd

An access control bypass and information disclosure vulnerability exists in the base AppArmor security profile configuration of Canonical snapd. The abstraction rules located in /etc/apparmor.d/abstractions/nss-systemd (inherited via ) inadvertently permit strictly confined snap applications, which lack the privileged account-control interface, to interact directly with the io.systemd.Multiplexer and io.systemd.NameServiceSwitch UNIX domain sockets under /run/systemd/userdb/. On systems where the systemd-userdbd service is installed and operational, the service fails to distinguish between an unconfined root user on the host system and a rest

• Auf 2.76+ubuntu24.04.1 aktualisieren

Invoking pathological inputs can lead to client panic in golang.org/x/crypto/ssh/agent

For certain crafted inputs, a 'ed25519.PrivateKey' was created by casting malformed wire bytes, leading to a panic when used.

Invoking VerifiedPublicKeyCallback permissions skip enforcement in golang.org/x/crypto/ssh

Previously, CVE-2024-45337 fixed an authorization bypass for misused ssh server configurations; if any other type of callback is passed other than public key, then the source-address validation would be skipped.

Invoking auth bypass via unenforced @revoked status in golang.org/x/crypto/ssh/knownhosts

Previously, a revoked 'SignatureKey' belonging to a CA was not correctly checked for revocation. Now, both the 'key' and 'key.SignatureKey' are checked for @revoked.

Invoking infinite loop on large channel writes in golang.org/x/crypto/ssh

When writing data larger than 4GB in a single Write call on an SSH channel, an integer overflow in the internal payload size calculation caused the write loop to spin indefinitely, sending empty packets without making progress. The size comparison now uses int64 to prevent truncation.

Invoking bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh

The Verify() method for FIDO/U2F security key types ([email protected], [email protected]) did not check the User Presence flag. Signatures generated without physical touch were accepted, allowing unattended use of a hardware security key. To restore the previous behavior, return a "no-touch-required" extension in Permissions.Extensions from PublicKeyCallback.

Invoking pathological RSA/DSA parameters may cause DoS in golang.org/x/crypto/ssh

The RSA and DSA public key parsers did not enforce size limits on key parameters. A crafted public key with an excessively large modulus or DSA parameter could cause several minutes of CPU consumption during signature verification. This could be triggered by unauthenticated clients during public key authentication. RSA moduli are now limited to 8192 bits, and DSA parameters are validated per FIPS 186-2.

Invoking client can cause server deadlock on unexpected responses in golang.org/x/crypto/ssh

A malicious SSH peer could send unsolicited global request responses to fill an internal buffer, blocking the connection's read loop. The blocked goroutine could not be released by calling Close(), resulting in a resource leak per connection. Unsolicited global responses are now discarded.

Invoking memory leak when rejecting channels can lead to DoS in golang.org/x/crypto/ssh

An authenticated SSH client that repeatedly opened channels which were rejected by the server caused unbounded memory growth, eventually crashing the server process and affecting all connected users. Rejected channels are now properly removed from the connection's internal state and released for garbage collection.

Invoking server panic during CheckHostKey/Authenticate in golang.org/x/crypto/ssh

SSH servers which use CertChecker as a public key callback without setting IsUserAuthority or IsHostAuthority could be caused to panic by a client presenting a certificate. CertChecker now returns an error instead of panicking when these callbacks are nil.

Invoking bypass of certificate restrictions in golang.org/x/crypto/ssh

When an SSH server authentication callback returned PartialSuccessError with non-nil Permissions, those permissions were silently discarded, potentially dropping certificate restrictions such as force-command after a second factor succeeded. Returning non-nil Permissions with PartialSuccessError now results in a connection error.

Invoking byte arithmetic causes underflow and panic in golang.org/x/crypto/ssh

An incorrectly placed cast from bytes to int allowed for server-side panic in the AES-GCM packet decoder for well-crafted inputs.

Invoking agent constraints dropped when forwarding keys in golang.org/x/crypto/ssh/agent

When adding a key to a remote agent constraint extensions such as [email protected] were not serialized in the request. Destination restrictions were silently stripped when forwarding keys, allowing unrestricted use of the key on the remote host. The client now serializes all constraint extensions. Additionally, the in-memory keyring returned by NewKeyring() now rejects keys with unsupported constraint extensions instead of silently ignoring them.

Invoking key constraints not enforced in golang.org/x/crypto/ssh/agent

The in-memory keyring returned by NewKeyring() silently accepted keys with the ConfirmBeforeUse constraint but never enforced it. The key would sign without any confirmation prompt, with no indication to the caller that the constraint was not in effect. NewKeyring() now returns an error when unsupported constraints are requested.

Local Privilege Escalation in snapd

Local privilege escalation in snapd on Linux allows local attackers to get root privilege by re-creating snap's private /tmp directory when systemd-tmpfiles is configured to automatically clean up this directory. This issue affects Ubuntu 16.04 LTS, 18.04 LTS, 20.04 LTS, 22.04 LTS, and 24.04 LTS.

• Auf 2.73+ubuntu24.04.2 aktualisieren

Malformed constraint may cause denial of service in golang.org/x/crypto/ssh/agent

SSH Agent servers do not validate the size of messages when processing new identity requests, which may cause the program to panic if the message is malformed due to an out of bounds read.

Unbounded memory consumption in golang.org/x/crypto/ssh

SSH servers parsing GSSAPI authentication requests do not validate the number of mechanisms specified in the request, allowing an attacker to cause unbounded memory consumption.