CVE-2026-66391 Overview
CVE-2026-66391 is a vulnerability in Apache Wicket caused by the use of insufficiently random values, resulting in a protection mechanism failure. The flaw is classified under [CWE-330] (Use of Insufficiently Random Values). Affected releases include Apache Wicket 9.0.0 through 9.23.0 and 10.0.0 through 10.9.0. The Apache Wicket project recommends upgrading to version 10.10.0, which addresses the issue. The vulnerability is exploitable over the network without authentication or user interaction, impacting the confidentiality and integrity of affected applications.
Critical Impact
Predictable random values in Apache Wicket weaken protection mechanisms that rely on unguessable tokens, exposing web applications to token prediction and related bypass attacks.
Affected Products
- Apache Wicket 9.0.0 through 9.23.0
- Apache Wicket 10.0.0 through 10.9.0
- Web applications built on the affected Wicket versions
Discovery Timeline
- 2026-07-27 - CVE-2026-66391 published to NVD
- 2026-07-28 - Last updated in NVD database
Technical Details for CVE-2026-66391
Vulnerability Analysis
Apache Wicket is a component-based Java web framework used to build stateful server-side web applications. The framework relies on random values for security-sensitive functions such as session identifiers, CSRF tokens, component identifiers, and other unguessable references. When those values are generated using an insufficiently random source, an attacker can predict or narrow the value space and defeat the protection mechanism that depends on them.
The issue is exploitable remotely, requires no privileges, and requires no user interaction. Successful exploitation impacts confidentiality and integrity but not availability. The Apache Software Foundation classifies the flaw under [CWE-330], which covers cases where random values are used for security decisions but are produced by a weak or predictable source.
Root Cause
The root cause is the reliance on a random value generator that does not provide sufficient entropy for security-sensitive operations. Values that must be unpredictable can be inferred by an attacker who observes prior outputs or reproduces the generator state. As a result, protection mechanisms built on those tokens fail to withstand adversarial prediction.
Attack Vector
An unauthenticated remote attacker interacts with a Wicket-based web application over the network. By observing token issuance patterns or replaying computed values, the attacker predicts subsequent tokens used by the framework. Predicted tokens can then be substituted into requests to bypass safeguards that depend on their unguessability. Consult the Apache Security Announcement and the Openwall OSS Security Update for the vendor's technical description.
Detection Methods for CVE-2026-66391
Indicators of Compromise
- Repeated requests to Wicket application endpoints containing sequentially or statistically related token values.
- Unusual session or component identifier collisions in application logs.
- Successful actions performed with tokens that were not issued to the requesting client.
Detection Strategies
- Inventory deployed Apache Wicket versions across build manifests, container images, and application servers to identify releases in the 9.0.0–9.23.0 and 10.0.0–10.9.0 ranges.
- Correlate authentication, session, and CSRF failure events against source IPs to identify token guessing behavior.
- Add web application firewall rules that flag high-frequency requests carrying malformed or reused Wicket identifiers.
Monitoring Recommendations
- Ingest web server and application logs into a centralized analytics pipeline to detect token misuse patterns.
- Alert on spikes in 4xx responses tied to invalid session or component identifiers on Wicket endpoints.
- Track dependency versions continuously so newly disclosed Wicket advisories trigger review of running applications.
How to Mitigate CVE-2026-66391
Immediate Actions Required
- Upgrade Apache Wicket to version 10.10.0 or later on all affected applications.
- Invalidate existing sessions and rotate any long-lived tokens issued by vulnerable Wicket versions.
- Review application code for custom uses of Wicket's random value APIs and ensure they now rely on the patched implementation.
Patch Information
The Apache Wicket project has released version 10.10.0, which fixes the insufficient randomness issue. Users on the 9.x branch should plan a migration path to a fixed release. Refer to the Apache Security Announcement for the authoritative fix guidance and to the Openwall OSS Security Update for distribution notes.
Workarounds
- If immediate upgrade is not possible, place vulnerable Wicket applications behind a reverse proxy that enforces strict rate limiting on token-bearing endpoints.
- Shorten session lifetimes and token validity windows to reduce the value of any predicted token.
- Restrict network exposure of internal Wicket applications to trusted networks until patching completes.
# Configuration example: update Maven dependency to the fixed Apache Wicket release
mvn versions:set-property -Dproperty=wicket.version -DnewVersion=10.10.0
mvn -U clean verify
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
