Description
/bin/login in shadow 4.0.18.1 in Debian GNU/Linux, and probably other Linux distributions, allows local users in the utmp group to overwrite arbitrary files via a symlink attack on a temporary file referenced in a line (aka ut_line) field in a utmp entry.
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 | shadow | 1:4.1.1-6 | — |
| Debian 13 | shadow | 1:4.1.1-6 | — |
| Debian 12 | shadow | 1:4.1.1-6 | — |
| Debian 4.0 | shadow | 1:4.0.18.1-7+etch1 | DSA-1709-1 |
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
- Debian - Symlink In Login Arbitrary File Ownership EDB-7313 · local · Dec 1, 2008 · verified
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 1
- DSA-1709-1 shadow - privilege escalation Debian Security (DSA / DLA) · Mar 9, 2026
References
- 52200 vdb-entry
- http://bugs.debian.org/505271
- 32552 vdb-entry
- http://bugs.debian.org/332198
- debian-login-symlink(47037) vdb-entry
- GLSA-200903-24 vendor-advisory
- MDVSA-2009:062 vendor-advisory
- 20081130 /bin/login gives root to group utmp mailing-list
- 7313 exploit
- 4695 third-party-advisory
- http://bugs.debian.org/505071
- USN-695-1 vendor-advisory