Nginx
CVE-2014-3556
MEDIUM
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization Command injection prevention
MITRE ATT&CK
1 technique across 1 tactic: Execution The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Impact | CVSS score of 6.8 (MEDIUM). Attack characteristics: network attack vector, M complexity. EPSS exploitation probability: 48.17%. |
| Exploit ScenarioDerived | A remote attacker could inject arbitrary commands into system command execution by sending crafted requests to the affected application. |
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Alert meAnalysisAI
The STARTTLS implementation in mail/ngx_mail_smtp_handler.c in the SMTP proxy in nginx 1.5.x and 1.6.x before 1.6.1 and 1.7.x before 1.7.4 does not properly restrict I/O buffering, which allows. Rated medium severity (CVSS 6.8), this vulnerability is remotely exploitable. Epss exploitation probability 48.2%.
RemediationAI
A vendor patch is available. Apply the latest security update as soon as possible. Use parameterized APIs, avoid shell execution, validate input with strict allowlists.
Affects your stack
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Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
This vulnerability is classified as Command Injection (CWE-77), which allows attackers to inject arbitrary commands into system command execution. The STARTTLS implementation in mail/ngx_mail_smtp_handler.c in the SMTP proxy in nginx 1.5.x and 1.6.x before 1.6.1 and 1.7.x before 1.7.4 does not properly restrict I/O buffering, which allows man-in-the-middle attackers to insert commands into encrypted SMTP sessions by sending a cleartext command that is processed after TLS is in place, related to a "plaintext command injection" attack, a similar issue to CVE-2011-0411. Affected products include: F5 Nginx. Version information: before 1.6.1.
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Severity by source
AV:N/AC:M/Au:N/C:P/I:P/A:P
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
DescriptionCVE.org
The STARTTLS implementation in mail/ngx_mail_smtp_handler.c in the SMTP proxy in nginx 1.5.x and 1.6.x before 1.6.1 and 1.7.x before 1.7.4 does not properly restrict I/O buffering, which allows man-in-the-middle attackers to insert commands into encrypted SMTP sessions by sending a cleartext command that is processed after TLS is in place, related to a "plaintext command injection" attack, a similar issue to CVE-2011-0411.
Threat Intelligence Overview
NVD
CVE.org
EPSS
How this decision was reached
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What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
OS command injection occurs when an application passes unsanitized user input directly into system shell commands.
Affected Products (CPE)CVE.org
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GitHub PoC
Exploit-DB