CVE-2017-9525

Publication date 9 June 2017

Last updated 24 July 2024

Ubuntu priority

Low

Why this priority?

Cvss 3 Severity Score

6.7 · Medium

Score breakdown

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.

Read the notes from the security team

Status

Package Ubuntu Release Status
cron 25.04 plucky
Not affected
24.10 oracular
Not affected
24.04 LTS noble
Not affected
23.10 mantic
Not affected
23.04 lunar
Not affected
22.10 kinetic
Not affected
22.04 LTS jammy
Not affected
21.10 impish
Not affected
21.04 hirsute
Not affected
20.10 groovy
Not affected
20.04 LTS focal
Not affected
19.10 eoan
Not affected
19.04 disco Ignored end of life
18.10 cosmic Ignored end of life
18.04 LTS bionic
Fixed 3.0pl1-128.1ubuntu1.2
17.10 artful Ignored end of life
17.04 zesty Ignored end of life
16.10 yakkety Ignored end of life
16.04 LTS xenial
14.04 LTS trusty
Vulnerable

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Notes

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.

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package Patch details
cron

Severity score breakdown

Parameter Value
Base score 6.7 · Medium
Attack vector Local
Attack complexity Low
Privileges required High
User interaction None
Scope Unchanged
Confidentiality High
Integrity impact High
Availability impact High
Vector CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

References

Related Ubuntu Security Notices (USN)

Other references