[Bug 2134446] [NEW] Upgrade to Ubuntu 26.04 LTS set invalid channel for seeded snaps

[Jeremy Bícha]

*** This bug is a security vulnerability ***

Public security bug reported:

Test Case
=========
Install Ubuntu Desktop 25.10
Log in. Install all updates. Restart.
Log in. Run update-manager -d. Follow the prompts to upgrade to Ubuntu 26.04 LTS.

What Happens
============
All seeded snaps are set to track "stable/ubuntu-26.04 LTS". That is an invalid target.

(excerpt)
$ snap info firefox
name:      firefox
summary:   Mozilla Firefox web browser
description: |
  Firefox is a powerful, extensible web browser with support for modern web
  application technologies.
tracking:     latest/stable/ubuntu-26.04 LTS

I only noticed this issue because I wondered why I still had Firefox 144
on an Ubuntu 26.04 LTS devel instance, even though Firefox 146 is
scheduled for release tomorrow.

Nothing in the system warns about this unless you happen to run a
command like this manually:

$ snap refresh firefox
error: requested a non-existing branch on latest/stable for snap "firefox": ubuntu-26.04 LTS

I am setting the severity to Critical because this prevents nearly
everyone using Firefox from receiving security updates. (Mitigated
because relatively few people are running Ubuntu 26.04 LTS now, but it
is being used by developers and very early adopters.) I did not check if
upgrades to Ubuntu 24.04 LTS are affected, but I hope we would have seen
bug reports if that were true.

Workaround
==========
I requested a simple command to fix this in LP: #2134444

Otherwise, it's tedious to update all your affected seeded snaps manually. You can find a list at
https://cdimage.ubuntu.com/daily-live/current/resolute-desktop-amd64.manifest
If you're using a different flavor of Ubuntu, use the appropriate manifest instead:
https://cdimage.ubuntu.com/edubuntu/daily-live/current/resolute-desktop-amd64.manifest

sudo snap refresh --amend --channel=1/stable/ubuntu-26.04 desktop-security-center
sudo snap refresh --channel=stable/ubuntu-26.04 firefox

Do that for all the seeded snaps to match what you see at the bottom of
the manifest file. Thunderbird isn't installed if you didn't choose the
full install option for Ubuntu Desktop.

ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: ubuntu-release-upgrader-core 1:26.04.2
ProcVersionSignature: Ubuntu 6.17.0-7.7-generic 6.17.2
Uname: Linux 6.17.0-7-generic x86_64
ApportVersion: 2.33.1-0ubuntu3
Architecture: amd64
CasperMD5CheckResult: pass
CrashDB: ubuntu
CrashReports: 644:0:110:0:2025-12-08 18:02:11.640000000 -0500:2025-12-08 22:49:37.929000000 -0500:/var/crash/kdump_lock
CurrentDesktop: ubuntu:GNOME
Date: Mon Dec  8 23:02:49 2025
InstallationDate: Installed on 2025-10-24 (45 days ago)
InstallationMedia: Ubuntu 25.10 "Questing Quokka" - Beta amd64 (20250917.2)
PackageArchitecture: all
ProcEnviron:
 LANG=en_US.UTF-8
 PATH=(custom, no user)
 SHELL=/bin/bash
 TERM=xterm-256color
 XDG_RUNTIME_DIR=<set>
SourcePackage: ubuntu-release-upgrader
Symptom: ubuntu-release-upgrader
UpgradeStatus: Upgraded to resolute on 2025-12-09 (0 days ago)
VarLogDistupgradeTermlog:

** Affects: ubuntu-release-upgrader (Ubuntu)
     Importance: Critical
         Status: New


** Tags: amd64 apport-bug dist-upgrade resolute wayland-session

** Information type changed from Public to Public Security

-- 
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https://bugs.launchpad.net/bugs/2134446

Title:
  Upgrade to Ubuntu 26.04 LTS set invalid channel for seeded snaps

Status in ubuntu-release-upgrader package in Ubuntu:
  New

Bug description:
  Test Case
  =========
  Install Ubuntu Desktop 25.10
  Log in. Install all updates. Restart.
  Log in. Run update-manager -d. Follow the prompts to upgrade to Ubuntu 26.04 LTS.

  What Happens
  ============
  All seeded snaps are set to track "stable/ubuntu-26.04 LTS". That is an invalid target.

  (excerpt)
  $ snap info firefox
  name:      firefox
  summary:   Mozilla Firefox web browser
  description: |
    Firefox is a powerful, extensible web browser with support for modern web
    application technologies.
  tracking:     latest/stable/ubuntu-26.04 LTS

  I only noticed this issue because I wondered why I still had Firefox
  144 on an Ubuntu 26.04 LTS devel instance, even though Firefox 146 is
  scheduled for release tomorrow.

  Nothing in the system warns about this unless you happen to run a
  command like this manually:

  $ snap refresh firefox
  error: requested a non-existing branch on latest/stable for snap "firefox": ubuntu-26.04 LTS

  I am setting the severity to Critical because this prevents nearly
  everyone using Firefox from receiving security updates. (Mitigated
  because relatively few people are running Ubuntu 26.04 LTS now, but it
  is being used by developers and very early adopters.) I did not check
  if upgrades to Ubuntu 24.04 LTS are affected, but I hope we would have
  seen bug reports if that were true.

  Workaround
  ==========
  I requested a simple command to fix this in LP: #2134444

  Otherwise, it's tedious to update all your affected seeded snaps manually. You can find a list at
  https://cdimage.ubuntu.com/daily-live/current/resolute-desktop-amd64.manifest
  If you're using a different flavor of Ubuntu, use the appropriate manifest instead:
  https://cdimage.ubuntu.com/edubuntu/daily-live/current/resolute-desktop-amd64.manifest

  sudo snap refresh --amend --channel=1/stable/ubuntu-26.04 desktop-security-center
  sudo snap refresh --channel=stable/ubuntu-26.04 firefox

  Do that for all the seeded snaps to match what you see at the bottom
  of the manifest file. Thunderbird isn't installed if you didn't choose
  the full install option for Ubuntu Desktop.

  ProblemType: Bug
  DistroRelease: Ubuntu 26.04
  Package: ubuntu-release-upgrader-core 1:26.04.2
  ProcVersionSignature: Ubuntu 6.17.0-7.7-generic 6.17.2
  Uname: Linux 6.17.0-7-generic x86_64
  ApportVersion: 2.33.1-0ubuntu3
  Architecture: amd64
  CasperMD5CheckResult: pass
  CrashDB: ubuntu
  CrashReports: 644:0:110:0:2025-12-08 18:02:11.640000000 -0500:2025-12-08 22:49:37.929000000 -0500:/var/crash/kdump_lock
  CurrentDesktop: ubuntu:GNOME
  Date: Mon Dec  8 23:02:49 2025
  InstallationDate: Installed on 2025-10-24 (45 days ago)
  InstallationMedia: Ubuntu 25.10 "Questing Quokka" - Beta amd64 (20250917.2)
  PackageArchitecture: all
  ProcEnviron:
   LANG=en_US.UTF-8
   PATH=(custom, no user)
   SHELL=/bin/bash
   TERM=xterm-256color
   XDG_RUNTIME_DIR=<set>
  SourcePackage: ubuntu-release-upgrader
  Symptom: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to resolute on 2025-12-09 (0 days ago)
  VarLogDistupgradeTermlog:

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