# Software Engineering Institute

## Race condition in periodic

#### Vulnerability Note VU#626919

Original Release Date: 2000-11-13 | Last Revised: 2001-03-28

### Overview

A race condition in the 'periodic' script allows local files to be overwritten. We believe that 'periodic' is typically used only with FreeBSD systems, though it may be installed on other systems.

### Description

 'periodic' is a script used in conjunction with cron to execute jobs at specified intervals. During ordinary work, periodic creates temporary files with predictable names of the form /tmp/periodic.$PID where$PID is the process identifier of the process running periodic. Because periodic is called by cron it runs with enhanced privileges. By polling the system for an executing instance of periodic, an intruder can exploit a race condition and create a symbolic link from /tmp/periodic.\$PID to a file of the intruders choosing. The target file will be overwritten.

### Impact

 An attacker or intruder who has write access to the local file system and who can discover the PIDs of other processes (both capabilities are typical for ordinary local users) can overwrite any fileon the system regardless of the permissions on the file. This ability can be leveraged to gain root access in many circumstances.

### Solution

 Apply a patch from your vendor.

626919

### FreeBSD Affected

Notified:  November 02, 2000 Updated: November 13, 2000

Affected

### Vendor Statement

We have not received a statement from the vendor.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### Apple Not Affected

Notified:  November 02, 2000 Updated: November 13, 2000

Not Affected

### Vendor Statement

Mac OS X does not contain the 'periodic' application and is not vulnerable.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

### BSDI Not Affected

Notified:  November 02, 2000 Updated: November 13, 2000

Not Affected

### Vendor Statement

No versions of BSD/OS are vulnerable to this problem. It does appear to be a problem with the new FreeBSD version and is not present in the original scripts that were part of 4.4BSD.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

### Compaq Computer Corporation Not Affected

Notified:  November 02, 2000 Updated: November 13, 2000

Not Affected

### Vendor Statement

We don't use/ship with this.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### IBM Not Affected

Notified:  November 02, 2000 Updated: January 10, 2001

Not Affected

### Vendor Statement

IBM's AIX operating system is not vulnerable to this exploit.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### NetBSD Not Affected

Updated:  November 02, 2000

Not Affected

### Vendor Statement

The problem reported does not apply to NetBSD, as no version of NetBSD uses FreeBSD's "periodic" script for scheduling periodic tasks.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

### OpenBSD Not Affected

Notified:  November 01, 2000 Updated: November 13, 2000

Not Affected

### Vendor Statement

As far as we know [periodic is FreeBSD specific]. We have various cron jobs, but we've done extensive work to fix security issues in them.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### Caldera Unknown

Notified:  November 02, 2000 Updated: November 13, 2000

Unknown

### Vendor Statement

We have not received a statement from the vendor.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### Data General Unknown

Notified:  November 02, 2000 Updated: November 13, 2000

Unknown

### Vendor Statement

We have not received a statement from the vendor.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### Debian Unknown

Notified:  November 02, 2000 Updated: November 13, 2000

Unknown

### Vendor Statement

We have not received a statement from the vendor.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### Fujitsu Unknown

Notified:  November 02, 2000 Updated: November 13, 2000

Unknown

### Vendor Statement

We have not received a statement from the vendor.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### Hewlett Packard Unknown

Notified:  November 02, 2000 Updated: November 13, 2000

Unknown

### Vendor Statement

We have not received a statement from the vendor.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### NCR Unknown

Notified:  November 02, 2000 Updated: November 13, 2000

Unknown

### Vendor Statement

We have not received a statement from the vendor.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### NEC Unknown

Notified:  November 02, 2000 Updated: November 13, 2000

Unknown

### Vendor Statement

We have not received a statement from the vendor.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### RedHat Unknown

Notified:  November 02, 2000 Updated: November 13, 2000

Unknown

### Vendor Statement

We have not received a statement from the vendor.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### SCO Unknown

Notified:  November 02, 2000 Updated: November 13, 2000

Unknown

### Vendor Statement

We have not received a statement from the vendor.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### SGI Unknown

Notified:  November 02, 2000 Updated: November 13, 2000

Unknown

### Vendor Statement

We have not received a statement from the vendor.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### Sequent Unknown

Notified:  November 02, 2000 Updated: November 13, 2000

Unknown

### Vendor Statement

We have not received a statement from the vendor.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes the 'periodic' script is normally used only with FreeBSD.

### Sony Unknown

Notified:  November 02, 2000 Updated: November 13, 2000

Unknown

### Vendor Statement

We have not received a statement from the vendor.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### Sun Unknown

Notified:  November 02, 2000 Updated: November 13, 2000

Unknown

### Vendor Statement

We have not received a statement from the vendor.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### Unisys Unknown

Notified:  November 02, 2000 Updated: November 13, 2000

Unknown

### Vendor Statement

We have not received a statement from the vendor.

### Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

CERT/CC believes that the 'periodic' script is normally used only with FreeBSD.

### CVSS Metrics

Group Score Vector
Base
Temporal
Environmental

### Acknowledgements

Our thanks to David Lary of SecureWorks for reporting this vulnerability to us and providing technical detail.

This document was written by Shawn Hernan.

### Other Information

 CVE IDs: CVE-2000-0890 Severity Metric: 0.21 Date Public: 2000-11-13 Date First Published: 2000-11-13 Date Last Updated: 2001-03-28 04:25 UTC Document Revision: 14