CVE-2021-3493

Ubuntu OverlayFS 로컬 권한 상승

영향을 받는 버전

• Ubuntu 20.10
• Ubuntu 20.04 LTS
• Ubuntu 19.04
• Ubuntu 18.04 LTS
• Ubuntu 16.04 LTS
• Ubuntu 14.04 ESM

사용법

• gcc exploit.c -o exploit
• ./exploit

설명

"Ubuntu specific issue in the overlayfs file system in the Linux kernel where it did not properly validate the application of file system capabilities with respect to user namespaces. A local attacker could use this to gain elevated privileges, due to a patch carried in Ubuntu to allow unprivileged overlayfs mounts." - Ubuntu 보안

Linux 5.11에서 수정됨

참고 자료

• https://ssd-disclosure.com/ssd-advisory-overlayfs-pe/
• https://ubuntu.com/security/CVE-2021-3493
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7c03e2cda4a584cadc398e8f6641ca9988a39d52
• https://www.openwall.com/lists/oss-security/2021/04/16/1

면책 조항

저는 이 익스플로잇의 작성자가 아닙니다. 여기에서 찾은 PoC를 어떤 식으로든 수정하지 않았습니다: https://ssd-disclosure.com/ssd-advisory-overlayfs-pe/.