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 architectural sandboxing assumptions, drop intended restriction policies, or execute privileged actions inside the container namespace that should otherwise be strictly blocked. The vulnerability has been resolved by hardening the seccomp template engine to block the execution and creation of setuid executables by sandboxed snap processes.

Hi everyone,

Qualys discovered another Local Privilege Escalation (LPE) in snapd snap-confine, via Capabilities misconfiguration. Qualys will send an email on top of this one with their report, but in the meantime, for this vulnerability we assigned CVE-2026-8933, with CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H 7.8 HIGH

The upstream version of snapd containing the fix will be 2.76.1.

Also in this version we are fixing/disclosing other two vulnerabilities - CVE-2024-5300 AppArmor Base Profile Misconfiguration in snapd Permits Confined Snaps Unauthorized Access to Hashed Passwords via systemd-userdbd CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N 5.6 MEDIUM Credits: James Henstridge

- CVE-2026-15226 snapd snap-confine Sandbox Confinement Bypass via Omission of setuid Restriction in Seccomp Templates CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N 8.4 HIGH Credits: Zygmunt Krynicki

In Ubuntu those fixes will land in:

Xenial (16.04): snapd - 2.61.4ubuntu0.16.04.1+esm4 Bionic (18.04): snapd - 2.61.4ubuntu0.18.04.1+esm4 Focal (20.04): snapd - 2.67.1+20.04ubuntu1~esm3 Jammy (22.04): snapd - 2.76+ubuntu22.04.1 Noble (24.04): snapd - 2.76+ubuntu24.04.1 Resolute (26.04): snapd - 2.76+ubuntu26.04.3

And we will soon be publishing an advisory: https://ubuntu.com/security/notices/USN-8579-1

We want to thanks again Qualys, Zygmunt and James for their work and patience!

Thanks, Eduardo