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SYNTHESIS OF THE VULNERABILITY

An attacker can use a revoked DKIM key in order to stop
dkim-milter.

Gravity: 2/4

Consequences: denial of service of service

Provenance: internet client

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: 02/03/2009

IMPACTED PRODUCTS

– Debian Linux
– Fedora
– Unix - plateform

DESCRIPTION OF THE VULNERABILITY

The DKIM (DomainKeys Identified Mail) technology uses signatures
to authenticate emails. The public key used to check the signature
is stored in a DNS TXT record in the email sender domain. For
example:
mykey._domainkey IN TXT "g=; k=rsa; p=the-key"
When the key is revoked, the "p=" field is empty:
myrevokedkey._domainkey IN TXT "g=; k=rsa; p=the-key"

The dkim-milter program is a DKIM filter for Sendmail.

However, when an email is signed with a revoked key (with an empty
"p=" field), an assertion error occurs in dkim-milter.

An attacker can therefore use a revoked DKIM key in order to stop
dkim-milter.

CHARACTERISTICS

Identifiers: 2508602, FEDORA-2009-2374, VIGILANCE-VUL-8499

http://vigilance.fr/vulnerability/dkim-milter-denial-of-service-8499