CVE-2026-4405 Overview
CVE-2026-4405 is an information disclosure vulnerability in IBM Concert versions 1.0 through 3.0.0. The application permits web page content to be stored in local browser cache without appropriate restrictions. Another user on the same system can read this cached data, exposing information intended only for the authenticated session. The weakness is tracked under [CWE-525: Use of Web Browser Cache Containing Sensitive Information]. Exploitation requires local access to the system where IBM Concert was used.
Critical Impact
A local user can read cached web content belonging to another user, leading to disclosure of session-related or application data.
Affected Products
- IBM Concert 1.0
- IBM Concert 2.x
- IBM Concert through 3.0.0
Discovery Timeline
- 2026-10-19 - CVE CVE-2026-4405 published to NVD
- 2026-10-19 - Last updated in NVD database
Technical Details for CVE-2026-4405
Vulnerability Analysis
IBM Concert serves web pages without directives that prevent client-side caching of sensitive responses. Browsers store rendered pages, HTML fragments, and associated resources in the local file system cache. A separate user account on the same host can navigate to those cache files and inspect their contents. The disclosed data may include application state, user context, or operational information that the authenticated user viewed during a Concert session.
The scope is limited to confidentiality. The flaw does not permit modification of Concert data, authentication bypass, or remote exploitation. An attacker must already have a valid local account on the shared system, which constrains practical exposure to shared workstations, jump hosts, and multi-user environments.
Root Cause
The root cause is missing or insufficient HTTP cache-control headers on responses that render sensitive content. Without directives such as Cache-Control: no-store and Pragma: no-cache, browsers treat the responses as cacheable. Cached artifacts persist on disk under per-browser profile directories, where file permissions may not isolate them from other local accounts.
Attack Vector
Exploitation requires local filesystem access on a host where a user previously accessed IBM Concert in a browser. The attacker enumerates browser cache directories under the victim's profile path and parses stored responses to extract Concert web content. No network interaction or user interaction with the attacker is required.
No verified proof-of-concept code is available for CVE-2026-4405. See the IBM Support Page for vendor technical details.
Detection Methods for CVE-2026-4405
Indicators of Compromise
- Presence of IBM Concert URLs or hostnames inside browser cache directories owned by other users.
- Access events on browser cache files by accounts that did not originate the Concert session.
- Unexpected file reads under ~/.cache/, %LOCALAPPDATA%\...\Cache, or equivalent per-browser paths.
Detection Strategies
- Audit shared endpoints for cross-user access to browser profile directories using filesystem auditing.
- Review web proxy or EDR telemetry for IBM Concert HTTP responses lacking no-store or private cache directives.
- Correlate interactive logons on shared hosts with subsequent reads of another user's browser cache files.
Monitoring Recommendations
- Enable file integrity and access monitoring on browser cache paths across multi-user systems that reach IBM Concert.
- Alert when a non-owner process or user reads files under another account's browser profile directory.
- Track IBM Concert version inventory to confirm all instances are patched above 3.0.0.
How to Mitigate CVE-2026-4405
Immediate Actions Required
- Upgrade IBM Concert to a fixed release above 3.0.0 as published on the IBM Support Page.
- Instruct users of shared systems to clear browser caches after Concert sessions until patching is complete.
- Restrict IBM Concert use to single-user workstations where feasible.
Patch Information
IBM has published remediation guidance for CVE-2026-4405 on the IBM Support Page. Apply the vendor-supplied update to IBM Concert versions 1.0 through 3.0.0.
Workarounds
- Configure browsers in shared environments with policies that disable disk caching for the IBM Concert origin.
- Enforce per-user permissions on browser profile directories so other local accounts cannot read cache files.
- Use private or incognito browsing sessions for IBM Concert access on multi-user systems.
# Example browser cache cleanup on Linux after Concert use
rm -rf ~/.cache/google-chrome/Default/Cache/*
rm -rf ~/.cache/mozilla/firefox/*.default-release/cache2/*
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
