Description
The overlayfs implementation in the Linux kernel through 4.5.2 does not properly maintain POSIX ACL xattr data, which allows local users to gain privileges by leveraging a group-writable setgid directory.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | linux | 4.5.1-1 | — |
| Debian 13 | linux | 4.5.1-1 | — |
| Debian 12 | linux | 4.5.1-1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 14.04 LTS | linux | 3.13.0-79.123 | USN-2907-1 |
| Ubuntu 14.04 LTS | linux-lts-utopic | 3.16.0-62.82~14.04.1 | USN-2909-1 |
| Ubuntu 14.04 LTS | linux-lts-vivid | 3.19.0-51.57~14.04.1 | USN-2910-1 |
| Ubuntu 14.04 LTS | linux-lts-wily | 4.2.0-30.35~14.04.1 | USN-2908-2 |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.
Exploit-DB 1
- Ubuntu 14.04/15.10 - User Namespace Overlayfs Xattr SetGID Privilege Escalation EDB-41762 · local · Nov 22, 2016
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 4
- USN-2907-1 linux vulnerabilities Ubuntu Security Notices (USN) · Apr 22, 2026
- USN-2908-2 linux-lts-wily vulnerabilities Ubuntu Security Notices (USN) · Feb 10, 2026
- USN-2909-1 linux-lts-utopic vulnerabilities Ubuntu Security Notices (USN) · Feb 10, 2026
- USN-2910-1 linux-lts-vivid vulnerabilities Ubuntu Security Notices (USN) · Feb 10, 2026
References
- http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=e9f57ebcba563e0cd532926cab83c92bb4d79360
- http://people.canonical.com/~ubuntu-security/cve/2016/CVE-2016-1575.html
- https://launchpad.net/bugs/1534961
- http://www.halfdog.net/Security/2016/UserNamespaceOverlayfsXattrSetgidPrivilegeEscalation/
- [oss-security] 20160224 User Namespaces Overlayfs Xattr Setgid Privilege Escalation: Overlayfs mailing-list
- [oss-security] 20211018 Re: CVE-2021-3847: OverlayFS - Potential Privilege Escalation using overlays copy_up mailing-list