CVE-2003-0540
NVD-CWE-OtherPublished: August 27, 2003· Updated: Jun 16, 2026
Official Description
The address parser code in Postfix 1.1.12 and earlier allows remote attackers to cause a denial of service (lock) via (1) a malformed envelope address to a local host that would generate a bounce and contains the ".!" string in the MAIL FROM or Errors-To headers, which causes nqmgr to lock up, or (2) via a valid MAIL FROM with a RCPT TO containing a ".!" string, which causes an instance of the SMTP listener to lock up.
Technical Analysis
CVE-2003-0540 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
A proof-of-concept (PoC) exploit exists for CVE-2003-0540. While not yet confirmed in active campaigns, the availability of PoC code increases exploitation risk substantially.
CVSS v3.1 Vector Breakdown
Affected Vendors & Products
Exploit & PoC Resources
Official Patches & Advisories
All References (26)
Quick Facts
Related CVEs (NVD-CWE-Other)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2003-0540 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts