Process-memory disclosure via circular-buffer index underflow
Published May 6, 2021 · Updated Aug 4, 2024
Out-of-bounds read in Exim before 4.94.2 allows remote attackers to disclose process memory through unauthenticated SMTP commands. In smtp_setup_msg, the HAD macro wraps smtp_ch_index to zero after a DATA command, and the error path reads smtp_connection_had[-1] before using that byte to index smtp_names. Disclosure depends on memory layout: Debian's tested build returns NONE, while other layouts can select an out-of-bounds string.
Summary
What happened
Out-of-bounds read in Exim before 4.94.2 allows remote attackers to disclose process memory through unauthenticated SMTP commands. In smtp_setup_msg, the HAD macro wraps smtp_ch_index to zero after a DATA command, and the error path reads smtp_connection_had[-1] before using that byte to index smtp_names. Disclosure depends on memory layout: Debian's tested build returns NONE, while other layouts can select an out-of-bounds string.
The record
- CVE
- CVE-2020-28023
- Published
- May 6, 2021
- Updated
- Aug 4, 2024
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-125, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 6, 2021CVE publishedPublication date reported by the CVE source.
- Aug 4, 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.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- Qualys SMTP command-sequence proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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