Public bug reported:
Updated to ubuntu 26 from 24 and tmux ssh stopped working for keys with
passphrase.
Environment
gcr4: 4.4.0.1-8 (Ubuntu 26.04 "Resolute", but see cross-distro report
below)
gnome-keyring: 50.0-1
openssh-client: 1:10.2p1-2ubuntu3.7
Session: Wayland (GNOME)
Summary gcr-ssh-agent hangs indefinitely when asked to sign an SSH auth request
with a passphrase-protected ed25519 private key. The spawned ssh-add child
process enters a busy loop (state R, ~100% CPU on one core) and never returns,
so the ssh client blocks forever waiting for the signature.
A second ed25519 key that has no passphrase works perfectly through the same
gcr-ssh-agent instance, so this is specific to passphrase-protected keys, not
ed25519 in general.
Steps to reproduce
Generate (or use an existing) passphrase-protected ed25519 key:
ssh-keygen -t ed25519 -f ~/.ssh/id_test (set a passphrase)
Make sure SSH_AUTH_SOCK points at gcr-ssh-agent
(/run/user/<uid>/gcr/ssh), and the key is known to the agent (ssh-add -l lists
its fingerprint).
ssh to any host that accepts this key: ssh -vvv user@host
Observed behaviour ssh -vvv output stops permanently at: debug3:
sign_and_send_pubkey: signing using ssh-ed25519 SHA256:... and never proceeds.
A child ssh-add <keyfile> process appears under gcr-ssh-agent's cgroup, in
running state, consuming ~100% of one CPU core, and never exits. Each new
connection attempt leaves another such process running, so they accumulate (I
found 8+ stuck processes after normal use, and the gcr-ssh-agent.service had
accumulated 20+ hours of CPU time).
Expected behaviour Either a GUI/terminal passphrase prompt appears and the
connection proceeds, or the agent fails fast with a clear error — not an
infinite spin.
What I tried (did not fix it)
Restarting gcr-ssh-agent.service after confirming DISPLAY and
WAYLAND_DISPLAY were present in its systemd --user environment (the first
failure happened to coincide with the service having started before those
variables were imported, but fixing that and restarting did not resolve the
hang).
Pre-storing the key's passphrase in the login keyring via
/usr/libexec/seahorse/ssh-askpass <keyfile> before connecting — the dialog
appeared, passphrase was entered, but a subsequent connection attempt still
spawned a spinning ssh-add.
Killing the stuck processes and restarting gcr-ssh-agent.service — the
next connection attempt reproduces the hang again immediately.
Workaround Setting IdentityAgent none for the affected Host in ~/.ssh/config
bypasses gcr-ssh-agent entirely for that key and falls back to a normal
terminal passphrase prompt, which works correctly.
Related reports This looks like the same issue reported independently on
openSUSE Tumbleweed (different distro, identical symptom and identical stuck
ssh -vvv log line):
https://forums.opensuse.org/t/gcr-ssh-agent-causes-ssh-hang-with-ed25519-key/189481
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: gcr4 4.4.0.1-8
ProcVersionSignature: Ubuntu 7.0.0-38.38-generic 7.0.14
Uname: Linux 7.0.0-38-generic x86_64
ApportVersion: 2.34.1-0ubuntu0.1
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Tue Oct 13 13:24:01 2026
InstallationDate: Installed on 2025-08-18 (421 days ago)
InstallationMedia: Ubuntu 24.04.3 LTS "Noble Numbat" - Release amd64
(20250805.1)
SourcePackage: gcr4
UpgradeStatus: Upgraded to resolute on 2026-10-12 (1 days ago)
** Affects: gcr4 (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute wayland-session
** Attachment added: "ssh_verbose_hang.log"
https://bugs.launchpad.net/bugs/2170680/+attachment/6008670/+files/ssh_verbose_hang.log
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https://bugs.launchpad.net/bugs/2170680
Title:
gcr-ssh-agent hangs/spins forever when signing with a passphrase-
protected ssh-ed25519 key
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