Linux Picks Up Fix For Latest "Confused Deputy" Weakness Going Back To 2.6.12 Kernel
Written by Michael Larabel in Linux Security on 26 May 2021 at 01:23 PM EDT. 2 Comments
LINUX SECURITY --
Merged today to Linux 5.13 Git and marked for back-porting to stable series is a new "confused deputy" weakness and affects kernels going back to Linux 2.6.12 from 2005.

Merged today is a proc code change to check writes against the file opener for the /proc/$pid/attr/ area where security attributes are handled for a given process.

As explained by Kees Cook of Google and longtime Linux kernel developer, "Fix another "confused deputy" weakness. Writes to /proc/$pid/attr/ files need to check the opener credentials, since these fds do not transition state across execve(). Without this, it is possible to trick another process (which may have different credentials) to write to its own /proc/$pid/attr/ files, leading to unexpected and possibly exploitable behaviors."

More details on the "confused deputy" weakness privilege escalation attacks via the kernel documentation or for a broader overview of the situation via Wikipedia.
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