On Mon, Aug 10, 2026 at 05:06:41PM +0300, Kostiantyn Kostiuk wrote: > Before this commit, when qmp_guest_ssh_add_authorized_keys adds an > SSH key for an existing local user, the agent (running as root) decides > whether to create the user's .ssh directory with a symlink-following > directory test, and then writes and chowns the authorized_keys file. > A local unprivileged user who owns their home directory can pre-stage > their .ssh directory (or the authorized_keys file) as a symbolic link > so that, when the host or operator triggers a key add for that user, > the root agent follows the link and transfers ownership of an arbitrary > root-owned file or directory to the unprivileged user, who can then rewrite > it to obtain root. > > Fixes: CVE-2026-12080 > Fixes: https://gitlab.com/qemu-project/qemu/-/work_items/3929 > > v1: https://patchew.org/QEMU/[email protected]/ > v2 -> v1: > Change effective user/group ID instead of checking for symlinks and > changing ownership of the file. > > v2: https://patchew.org/QEMU/[email protected] > v3 -> v2: > Deduplicate code. > Fail daemon when can't rollback effective user/group ID. > > Reported-by: Valentino Paulon <[email protected]> > Signed-off-by: Kostiantyn Kostiuk <[email protected]> > --- > qga/commands-posix-ssh.c | 66 ++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 66 insertions(+)
Reviewed-by: Daniel P. Berrangé <[email protected]> With regards, Daniel -- |: https://berrange.com ~~ https://hachyderm.io/@berrange :| |: https://libvirt.org ~~ https://entangle-photo.org :| |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :|
