USN-5292-1 fixed a vulnerability in snapd. Unfortunately that update introduced
a regression that could break the fish shell. This update fixes the problem.
We apologize for the inconvenience.
Original advisory details:
James Troup discovered that snap did not properly manage the permissions for
the snap directories. A local attacker could possibly use this issue to expose
sensitive information. (CVE-2021-3155)
Ian Johnson discovered that snapd did not properly validate content interfaces
and layout paths. A local attacker could possibly use this issue to inject
arbitrary AppArmor policy rules, resulting in a bypass of intended acc
snapd could be made to bypass intended access restrictions through snap content interfaces and layout paths
snapd 2.54.2 fails to perform sufficient validation of snap content interface and layout paths, resulting in the ability for snaps to inject arbitrary AppArmor policy rules via malformed content interface and layout declarations and hence escape strict snap confinement. Fixed in snapd versions 2.54.3+18.04, 2.54.3+20.04 and 2.54.3+21.10.1
snapd could be made to escalate privileges and run programs as administrator
snapd 2.54.2 did not properly validate the location of the snap-confine binary. A local attacker who can hardlink this binary to another location to cause snap-confine to execute other arbitrary binaries and hence gain privilege escalation. Fixed in snapd versions 2.54.3+18.04, 2.54.3+20.04 and 2.54.3+21.10.1
snapd could be made to escalate privileges and run programs as administrator
A race condition existed in the snapd 2.54.2 snap-confine binary when preparing a private mount namespace for a snap. This could allow a local attacker to gain root privileges by bind-mounting their own contents inside the snap's private mount namespace and causing snap-confine to execute arbitrary code and hence gain privilege escalation. Fixed in snapd versions 2.54.3+18.04, 2.54.3+20.04 and 2.54.3+21.10.1