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CVE-2026-61899 is a critical information disclosure vulnerability identified in the Apache Tapestry web framework. The flaw resides in the `tapestry-core` module and affects all versions from 5.5.0 up to, but not including, 5.9.1. Discovered by security researcher Ilyass El Hadi, this vulnerability allows a remote, unauthenticated attacker to download sensitive classpath assets by sending specially crafted URLs.
Apache Tapestry, like many Java web frameworks, includes a built-in asset pipeline designed to serve static resources such as CSS, JavaScript, and images that are bundled within JAR or WAR artifacts from the classpath. This pipeline maps URL fragments to classpath paths. The vulnerability arises because the framework fails to properly confine the resolution lookup to designated asset subdirectories (normally `/META-INF/assets` or the root package). When a request URL contains specially crafted path components, an attacker can navigate up the directory hierarchy or use alternative separator characters to access other classpath entries, effectively bypassing the “asset-only” allow-list.
This access-control failure in the asset-serving layer is categorized under CWE-200: Exposure of Sensitive Information to an Unauthorized Actor. The vulnerability is platform-agnostic, as it is rooted in Java-level path resolution rather than OS-level filesystem behavior. The information exposed can include internal framework configuration files, message bundles, template files, and compiled Java `.class` files containing hardcoded secrets, business logic, or framework-internal structure. An attacker can leverage this reconnaissance to identify exact library versions, custom package names, and class structures, which can then be used to chain other attacks such as deserialization flaws. No public exploit is currently available, and Apache has released version 5.9.1 to remediate the issue.
DailyCVE Form:
Platform: Apache Tapestry
Version: 5.5.0 – 5.9.0
Vulnerability: Classpath asset disclosure
Severity: Critical
Date: 2026-08-10
Prediction: Patch already available (5.9.1)
What Undercode Say:
The following analytics and commands can be used to assess and understand the exposure related to CVE-2026-61899.
Check Tapestry Version:
Check the version of tapestry-core in a Maven project mvn dependency:tree | grep tapestry-core For a deployed application, inspect the manifest or use: find /path/to/app -name "tapestry-core-.jar"
Test for Vulnerability (Educational Purposes Only):
Attempt to access a sensitive classpath resource (example - do not use maliciously) curl -v "http://target-app.example.com/assets/../WEB-INF/web.xml" curl -v "http://target-app.example.com/assets/../../META-INF/MANIFEST.MF"
Monitor for Suspicious Requests:
Monitor access logs for directory traversal patterns in asset URLs grep "assets/.." /var/log/tapestry/access.log grep "assets/%2e%2e" /var/log/tapestry/access.log
Exploit: (Educational Purposes!)
The core of the exploit lies in the failure of the asset-serving mechanism to validate and sanitize URL paths. An attacker can craft a URL that includes path traversal sequences (e.g., ../) to escape the intended asset directory and access arbitrary files from the application’s classpath.
Conceptual Attack Flow:
- The attacker identifies a target Apache Tapestry application.
- The attacker sends a GET request to an asset URL, such as
/assets/css/style.css. - The attacker modifies the URL to include path traversal sequences, for example:
/assets/../WEB-INF/web.xml. - Due to the vulnerability, the Tapestry framework resolves this path and serves the contents of `web.xml` instead of the intended asset.
- The attacker can then repeat this process to enumerate and download other sensitive files from the classpath, including configuration files and compiled class files.
Protection:
The primary and recommended mitigation is to upgrade to Apache Tapestry version 5.9.1 or later, which contains the fix for this vulnerability.
If an immediate upgrade is not possible, consider the following workarounds:
Web Application Firewall (WAF): Deploy or update WAF rules to block requests to asset URLs containing path traversal patterns such as ../, ..\, or URL-encoded variants.
Input Validation: Implement a custom filter or interceptor to validate and sanitize all incoming asset URLs, rejecting any that contain sequences attempting to traverse directories.
Network Segmentation: Ensure that the Tapestry application is not directly exposed to the public internet and is accessible only through a secure gateway that can filter malicious requests.
Impact:
Successful exploitation of CVE-2026-61899 can have severe consequences for an affected application:
Information Disclosure: Sensitive internal files such as web.xml, configuration properties, message bundles, and compiled Java classes can be exposed.
Reconnaissance: Attackers can map out the application’s internal structure, library versions, and custom packages, which provides critical intelligence for planning further, more damaging attacks.
Chain Attacks: The disclosed information can be used to exploit other vulnerabilities, such as deserialization flaws, potentially leading to Remote Code Execution (RCE).
Data Breach: Exposure of hardcoded secrets or business logic can directly lead to a data breach or compromise of the application’s integrity.
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Sources:
Reported By: nvd.nist.gov
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