SPF bypass via noncanonical SMTP message terminator
Published Dec 24, 2023 · Updated Aug 2, 2024
SMTP smuggling in sendmail 8.17.2 and earlier allows remote attackers to inject spoofed messages that bypass SPF authentication. The SMTP DATA parser accepts LF-dot-CRLF as an end-of-message marker instead of requiring CRLF-dot-CRLF, allowing attacker-controlled data to be parsed as a second message. Exploitation requires a sending server that preserves the noncanonical sequence and a receiving sendmail configuration that interprets it as a terminator.
Summary
What happened
SMTP smuggling in sendmail 8.17.2 and earlier allows remote attackers to inject spoofed messages that bypass SPF authentication. The SMTP DATA parser accepts LF-dot-CRLF as an end-of-message marker instead of requiring CRLF-dot-CRLF, allowing attacker-controlled data to be parsed as a second message. Exploitation requires a sending server that preserves the noncanonical sequence and a receiving sendmail configuration that interprets it as a terminator.
The record
- CVE
- CVE-2023-51765
- Published
- Dec 24, 2023
- Updated
- Aug 2, 2024
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-451, CWE-345, T1036
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Dec 24, 2023CVE publishedPublication date reported by the CVE source.
- Aug 2, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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What conditions does exploitation require?
What is affected?
Affected products and versions are unavailable in this record.
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
- SEC Consult SMTP smuggling proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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