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Vigil@nce: vixie-cron, changing timestamp

February 2010 by Vigil@nce

A local attacker can use vixie-cron to reset a file modification time.

- Severity: 1/4
- Consequences: data creation/edition
- Provenance: user shell
- Means of attack: 1 attack
- Ability of attacker: technician (2/4)
- Confidence: confirmed by the editor (5/5)
- Diffusion of the vulnerable configuration: high (3/3)
- Creation date: 24/02/2010

IMPACTED PRODUCTS

- Fedora
- Unix - plateform

DESCRIPTION OF THE VULNERABILITY

The utime() function changes the time of a file:
- actime : time of the last access
- modtime : time of the last modification

When a user edits its crontab via "crontab -e", vixie-cron creates a temporary file in /tmp, and uses utime() to reset its access and modification times (in order to easily detect that the file was changed). However, these changes are done with root privileges.

A local attacker can therefore edit his crontab, and create a symbolic link, in order to force vixie-cron to change times of a file.

CHARACTERISTICS

- Identifiers: CVE-2010-0424, FEDORA-2010-2751, VIGILANCE-VUL-9473
- Url: http://vigilance.fr/vulnerability/v...




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