Security readout for executives and security teams
An old flaw in the Sendmail mail server (versions 8.8.x and 8.9.2) let a remote sender crash or hang the service by sending an email with an unusually large number of headers. The impact is a denial of service on the mail relay, meaning messages stop flowing until the process is restarted. There is no data theft indicated, but email delivery availability is affected. Very narrow in 2026: exposure is limited to any residual internet-facing Sendmail 8.8.x or 8.9.2 instances, which are more than two decades out of support. Modern mail infrastructure will not be affected. Legacy Unix hosts, appliances, or air-gapped systems still running these versions would be the only realistic exposure surface. Low priority for modern environments. Treat as a legacy hygiene item: only relevant if the organization still operates Sendmail 8.8.x or 8.9.2, in which case replacement or upgrade of that obsolete mail server should be scheduled as part of routine lifecycle management. Mitigation focus: Upgrade any Sendmail 8.8.x or 8.9.2 hosts to a currently supported MTA release.; Retire legacy Sendmail installations in favor of a maintained mail platform where feasible.; Consult current vendor guidance before applying any changes to production mail servers..
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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CVE-1999-0393 mapping review
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Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
CNA and ADP enrichment extracted from CVE v5
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CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
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CWE details
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