SMTP process crash via stale regex captures
Published Oct 17, 2022 · Updated Nov 3, 2025
Use-after-free in Exim before 4.97 allows remote attackers to crash an SMTP process through messages on one connection. The SMTP message-reset path leaves $regex capture pointers referencing memory released after the prior message, then later expansion reuses them. The affected variables were introduced in 4.87, and exploitation requires content-scanning rules that populate and later expand regex captures across multiple messages; the observed consequence is often a segmentation fault.
Summary
What happened
Use-after-free in Exim before 4.97 allows remote attackers to crash an SMTP process through messages on one connection. The SMTP message-reset path leaves $regex capture pointers referencing memory released after the prior message, then later expansion reuses them. The affected variables were introduced in 4.87, and exploitation requires content-scanning rules that populate and later expand regex captures across multiple messages; the observed consequence is often a segmentation fault.
The record
- CVE
- CVE-2022-3559
- Published
- Oct 17, 2022
- Updated
- Nov 3, 2025
- Vendor
- LibSPF2 Project
- Product
- Exim
- Classifications
- CWE-119, CWE-416, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Oct 17, 2022CVE publishedPublication date reported by the CVE source.
- Nov 3, 2025Record updatedLatest update available in the CVE record.
Exploitability
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- Affected versionversion=n/a
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What is affected?
Published CVSS scores
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Attacks
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Technologies
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Your stack
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