CVE-2017-9525
Published: 9 June 2017
In the cron package through 3.0pl1-128 on Debian, and through 3.0pl1-128ubuntu2 on Ubuntu, the postinst maintainer script allows for group-crontab-to-root privilege escalation via symlink attacks against unsafe usage of the chown and chmod programs.
Priority
Low
CVSS 3 base score: 6.7
Status
| Package | Release | Status |
|---|---|---|
|
cron Launchpad, Ubuntu, Debian |
artful |
Ignored
(reached end-of-life)
|
| bionic |
Released
(3.0pl1-128.1ubuntu1.2)
|
|
| cosmic |
Ignored
(reached end-of-life)
|
|
| disco |
Ignored
(reached end-of-life)
|
|
| eoan |
Not vulnerable
(3.0pl1-134ubuntu1)
|
|
| focal |
Not vulnerable
(3.0pl1-134ubuntu1)
|
|
| groovy |
Not vulnerable
(3.0pl1-134ubuntu1)
|
|
| hirsute |
Not vulnerable
(3.0pl1-134ubuntu1)
|
|
| impish |
Not vulnerable
(3.0pl1-134ubuntu1)
|
|
| jammy |
Not vulnerable
(3.0pl1-134ubuntu1)
|
|
| precise |
Ignored
(end of ESM support, was needed)
|
|
| trusty |
Needed
|
|
| upstream |
Released
(3.0pl1-129)
|
|
| xenial |
Released
(3.0pl1-128ubuntu2+esm2)
|
|
| yakkety |
Ignored
(reached end-of-life)
|
|
| zesty |
Ignored
(reached end-of-life)
|
Notes
| Author | Note |
|---|---|
| jj | This appears to be mitigated by kernel symlink restrictions. The crontabs dir has the sticky bit set drwx-wx--T root crontab crontabs which means symlinks within the dir must have the same uid as the target. It is still possible that a cron package update could trigger this race. |
| seth-arnold | I believe that actually _exploiting_ the bug requires updating the cron package. So long as there's no updates for cron, the vulnerable code doesn't run. So if we find a second bug in cron then we really should fix the race condition at the same time, but so long as we don't push a cron update, the vulnerable code just plain doesn't run. the patch just narrows the time window for the race condition. |
References
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-9525
- http://www.openwall.com/lists/oss-security/2017/06/08/3
- http://bugs.debian.org/864466
- https://ubuntu.com/security/notices/USN-5259-1
- https://ubuntu.com/security/notices/USN-5259-2
- https://ubuntu.com/security/notices/USN-5259-3
- NVD
- Launchpad
- Debian