Exim Buffer Overflow Vulnerability
An issue was discovered in the base64d function in the SMTP listener in Exim before 4.90.1. By sending a handcrafted message, a buffer overflow may happen. This can be used to execute code remotely.
Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.
Exploitation probability EPSS · FIRST
Exploitation signals 5 / 5
- KEV catalog (CISA)03 Nov 2021
- Exploited in EUVD (ENISA)03 Nov 2021
- Used by ransomwareyes
- EPSS above 10 %82.1%
- No account, over the networkyes
What to do
Fix
Apply the vendor’s fix as soon as it is available.
CISA guidance: Apply updates per vendor instructions.
Meanwhile
Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.
Manufacturers (CRA)
Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained
Affected products
Open source packages OSV
Affected libraries according to OSV, with fixed versions.
Timeline
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Published
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Exploitation reported (ENISA)
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Added to the KEV catalog
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CISA remediation due date
-
EPSS peak: 82.1%
References
Other exploited vulnerabilities from the same vendor
- CVE-2010-4345Exim Privilege Escalation Vulnerability5.5 · Background exploitation
- CVE-2010-4344Exim Heap-Based Buffer Overflow Vulnerability8.5 · Background exploitation
- CVE-2019-16928Exim Out-of-bounds Write Vulnerability7.6 · Background exploitation
- CVE-2019-10149Exim Mail Transfer Agent (MTA) Improper Input Validation9.0 · Background exploitation