Apache Struts 2 Jakarta Multipart Parser Remote Code Execution (RCE) Vulnerability (CVE-2017-5638) Analysis and Mitigation Guide
Executive & SecOps Summary
SECOPS ASSESSMENTWeb applications built on Apache Struts 2.3.x (before 2.3.32) and 2.5.x (before 2.5.10.1)
Unauthenticated remote attackers can execute arbitrary OS commands with system privileges via crafted HTTP headers such as Content-Type
Immediately upgrade Apache Struts to a secure version (2.3.32, 2.5.10.1, or higher) and apply WAF rules to block malicious OGNL payloads
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
The most effective remediation is to upgrade Apache Struts to a non-vulnerable version (2.3.32 or 2.5.10.1 and above). For Maven-based projects, update the dependency in your 'pom.xml' file:
<!-- Example of updating struts2-core dependency in pom.xml -->
<dependency>
<groupId>org.apache.struts</groupId>
<artifactId>struts2-core</artifactId>
<version>2.5.30</version> <!-- Use the latest secure version -->
</dependency>2. Temporary Workaround & Hardening Configuration
If an immediate upgrade is not feasible, switch the multipart parser from Jakarta to another implementation (such as 'jakarta-stream') in your 'struts.xml' configuration, or configure your Web Application Firewall (WAF) to block requests containing OGNL patterns in HTTP headers.
<!-- Workaround: Switch multipart parser in struts.xml -->
<struts>
<constant name='struts.multipart.parser' value='jakarta-stream' />
</struts>3. Log Audit & IoC Verification Commands
Inspect web server access logs for suspicious strings such as '#cmd=', 'java.lang.ProcessBuilder', or 'ognl' within the Content-Type header to identify potential exploitation attempts.
# Search for malicious OGNL injection patterns in web server access logs
grep -Ei '(#cmd|multipart/form-data.*#|java\.lang\.ProcessBuilder|ognl)' /var/log/nginx/access.log /var/log/apache2/access.log 2>/dev/nullBlock Exploits Instantly with Managed Virtual Patching Rules
Can't patch production immediately? Deploy managed WAF rules at the edge to intercept RCE, SQLi, and deserialization payloads before they hit your origin server.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2017-5638) exists in the Jakarta Multipart parser, the default file upload handler in the Apache Struts 2 framework. Due to improper exception handling and error-message generation during file upload attempts, Struts attempts to parse and evaluate OGNL (Object-Graph Navigation Language) expressions contained within error messages. This allows user-controlled inputs from HTTP headers (such as Content-Type, Content-Disposition, or Content-Length) to be directly executed by the OGNL engine.
2. Exploitation Mechanics & Attack Scenario
An attacker sends a crafted HTTP request containing a malicious OGNL expression inside the 'Content-Type' header. When the Jakarta Multipart parser encounters an error (e.g., invalid file size or format), it triggers an exception. The framework's 'LocalizedTextUtil.findText' method is then called to process the error message, which inadvertently evaluates the attacker's OGNL payload. By manipulating the '#_memberAccess' object and utilizing 'ProcessBuilder', the attacker bypasses sandbox restrictions to execute arbitrary system commands.
3. Infrastructure & Business Impact
With a CVSS score of 9.8, this vulnerability is highly critical and has been actively exploited in the wild. Successful exploitation grants unauthenticated remote attackers full control over the target server. This can lead to sensitive database exposure, lateral movement within the internal network, deployment of ransomware, and complete compromise of the enterprise infrastructure.
Official Vendor Advisories & References
The Jakarta Multipart parser in Apache Struts 2 2.3.x before 2.3.32 and 2.5.x before 2.5.10.1 has incorrect exception handling and error-message generation during file-upload attempts, which allows remote attackers to execute arbitrary commands via a crafted Content-Type, Content-Disposition, or Content-Length HTTP header, as exploited in the wild in March 2017 with a Content-Type header containing a #cmd= string.
Frequently Asked SecOps Questions (CVE-2017-5638)
FAQQ1. How critical is CVE-2017-5638 and is it actively exploited in the wild?
CVE-2017-5638 is rated CVSS 9.8 (CRITICAL) with a 30-day EPSS exploitation probability of 100.0%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2017-5638?
Primary impacted vendors include apache across struts. Scope summary: Apache Struts versions 2.3.19 through 2.3.31, and 2.5 through 2.5.10
Q3. What temporary mitigations or workarounds exist for CVE-2017-5638 before patching?
[Mitigation] Immediately upgrade Apache Struts to a secure version (2.3.32, 2.5.10.1, or higher) and apply WAF rules to block malicious OGNL payloads Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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