CVE-2014-9116

What it actually does

Improper handling of a leading newline in an email header causes mutt_substrdup to perform an out-of-bounds read/write, resulting in a heap-based buffer overflow that crashes the process.

Why it matters to the business

Attackers can remotely crash the mail client on affected systems, producing immediate denial of service that disrupts email workflows and may require manual restarts or patching to restore service.

How an attack unfolds

An attacker crafts an email containing a header whose first character is a newline followed by an empty body and sends it to a victim using the vulnerable mutt client; when mutt parses the header the malformed input reaches write_one_header and mutt_substrdup, triggering the overflow and crash.

How to fix it

Upgrade mutt (and any dependent wordpress packages) to the versions listed in the fixed_versions field for each distribution; after upgrade, restart all mutt processes and verify the new binary no longer accepts the malformed header.

How to confirm the fix worked

Send a test message containing a leading-newline header to a lab instance running the patched mutt; confirm the client does not crash and that the version string matches the fixed release.

Typical attack path

1. Craft a minimal RFC-compliant message whose first header line begins with a bare newline and has no body content.
2. Deliver the message via SMTP or place it in a mailbox the victim will open with mutt.
3. Victim’s mutt client parses the header, calling write_one_header then mutt_substrdup with attacker-controlled length.
4. Heap buffer overflow occurs, process crashes, and email access is lost until restart.

How to detect it

Search mail-server and client logs for message deliveries that contain headers beginning with a literal newline; inspect any resulting crash dumps or segfault entries in system logs around the same timestamp.

• segfault.*mutt
• mutt_substrdup
• header with empty body

What your security team should do

• Immediately schedule patching of all Debian 11/12/13 wordpress and mutt packages to the versions containing 4.2.4+dfsg-1.
• Block or quarantine messages whose headers begin with a bare newline at the MTA if possible until patches are deployed.
• Add the supplied detection_iocs to SIEM rules and run historical searches for the past 90 days.