Debian Server restored after Compromise
July 13th, 2006
One core Debian server has been reinstalled after a compromise and services have been restored. On July 12th the host gluck.debian.org was compromised using a local root vulnerability in the Linux kernel. The intruder had access to the server using a compromised developer account.
At least one developer account was compromised a while ago and has been used by an attacker to gain access to the Debian server. A recently discovered local root vulnerability in the Linux kernel has then been used to gain root access to the machine.
At 02:43 UTC on July 12th suspicious mails were received and alarmed the Debian admins. The following investigation turned out that a developer account was compromised and that a local kernel vulnerability had been exploited to gain root access.
At 04:30 UTC on July 12th gluck has been taken offline and booted off trusted media. Other Debian servers have been locked down for further investigation whether they were compromised as well. They will be upgraded to a corrected kernel before they will be unlocked.
Due to the short window between exploiting the kernel and Debian
admins noticing, the attacker hadn't had time/inclination to cause
much damage. The only obviously compromised binary was
The compromised account did not have access to any of the restricted Debian hosts. Hence, neither the regular nor the security archive had a chance to be compromised.
An investigation of developer passwords revealed a number of weak passwords whose accounts have been locked in response.
The machine status is here.
The kernel vulnerability that has been used for this compromise is referenced as CVE-2006-2451. It only exists in the Linux kernel 2.6.13 up to versions before 22.214.171.124, and 2.6.16 before 126.96.36.199. The bug allows a local user to gain root privileges via the PR_SET_DUMPABLE argument of the prctl function and a program that causes a core dump file to be created in a directory for which the user does not have permissions.
The current stable release, Debian GNU/Linux 3.1 alias 'sarge', contains Linux 2.6.8 and is thus not affected by this problem. The compromised server ran Linux 188.8.131.52.
If you run Linux 2.6.13 up to versions before 184.108.40.206, or Linux 2.6.16 up to versions before 220.127.116.11, please update your kernel immediately.
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