Sendmail Trojan Horse Vulnerability



Date Discovered

October 8, 2002


Reportedly, the server hosting sendmail,, was compromised recently. It has been reported that the intruder made modifications to the source code of sendmail to include Trojan Horse code. Downloads of the sendmail source code from between September 28, 2002 and October 6, 2002 likely contain the trojan code. It has also been reported that versions of sendmail available via HTTP distribution on the Sendmail Consortium site are not affected. Reports say that the trojan will run once upon compilation of sendmail. Once the Trojan is executed, it attempts to connect to host ( on port 6667. Although unconfirmed, it has been reported that the service listening on port 6667 of host ( has been disabled. The Sendmail Consortium has signed all valid distributions of the sendmail software with the following PGP key: pub 1024R/678C0A03 2001-12-18 Sendmail Signing Key/2002 <sendmail@Sendmail.ORG> Key fingerprint = 7B 02 F4 AA FC C0 22 DA 47 3E 2A 9A 9B 35 22 45 Additionally, the following checksums have been made available to verify packages against: 73e18ea78b2386b774963c8472cbd309 sendmail.8.12.6.tar.gz cebe3fa43731b315908f44889d9d2137 sendmail.8.12.6.tar.Z 8b9c78122044f4e4744fc447eeafef34 sendmail.8.12.6.tar.sig

Technologies Affected

  • Sendmail Consortium Sendmail 8.12.6


Block external access at the network boundary, unless external parties require service.
Filter untrusted network traffic at border routers and network firewalls.

Run all software as a nonprivileged user with minimal access rights.
Perform all tasks with the minimal privileges possible to perform task.

The vendor has stated that the versions served via HTTP download are not affected, and the valid versions of sendmail for downloaded from They are available from the normal distribution channels and have the following MD5 checksums: 73e18ea78b2386b774963c8472cbd309 sendmail.8.12.6.tar.gz cebe3fa43731b315908f44889d9d2137 sendmail.8.12.6.tar.Z 8b9c78122044f4e4744fc447eeafef34 sendmail.8.12.6.tar.sig Additionally, they are signed with the Sendmail Consortium PGP Key.



Advisory released by CERT.

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