Unauthenticated command execution via stale TLS pointer
Published May 6, 2021 · Updated Aug 4, 2024
Use-after-free in Exim 4.90 through 4.94.1 allows remote attackers to execute commands as the exim user through crafted SMTP traffic. smtp_reset frees POOL_MAIN memory without clearing tls_write's static server_corked pointer, so later SMTP replies reuse an attacker-controlled gstring and buffer. Exploitation requires an OpenSSL build with STARTTLS and PIPELINING enabled and X_PIPE_CONNECT disabled; successful exploitation reads and writes heap memory before executing commands with Exim service privileges.
Summary
What happened
Use-after-free in Exim 4.90 through 4.94.1 allows remote attackers to execute commands as the exim user through crafted SMTP traffic. smtp_reset frees POOL_MAIN memory without clearing tls_write's static server_corked pointer, so later SMTP replies reuse an attacker-controlled gstring and buffer. Exploitation requires an OpenSSL build with STARTTLS and PIPELINING enabled and X_PIPE_CONNECT disabled; successful exploitation reads and writes heap memory before executing commands with Exim service privileges.
The record
- CVE
- CVE-2020-28018
- Published
- May 6, 2021
- Updated
- Aug 4, 2024
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-416, 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
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
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
- dorkerdevil CVE-2020-28018 Exim exploitfunctional · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo