CVE-2026-16967 is a high severity (CVSS 8.5) time-of-check to time-of-use race condition involving symbolic links in IBM i 7.3, 7.4, 7.5 and 7.6. A remote authenticated attacker could gain unauthorized access to system objects. IBM provides a PTF for each release under 5770-SS1, and the bulletin lists the numbers.
What's affected
IBM i 7.6, 7.5, 7.4 and 7.3, per IBM's bulletin and the NVD record. IBM lists these PTFs for 5770-SS1:
- IBM i 7.6: SJ10871
- IBM i 7.5: SJ10835
- IBM i 7.4: SJ10840
- IBM i 7.3: SJ10841
IBM says to address the issue now and recommends that users of unsupported IBM i releases move to a supported, fixed version.
How to check if you're exposed
IBM i 7.3 through 7.6 are all in scope, so every supported and recently supported release needs a look. On each partition, confirm the installed release and then check whether the PTF for your release is loaded. From a command line:
DSPPTF LICPGM(5770SS1)
Look for the PTF number listed for your release in the table above, with a status of Applied or Permanently applied. You can also use option 10 of GO LICPGM to confirm the release. Do this on every LPAR, including test and recovery systems, because they are often patched last.
What to do now
- List every IBM i partition and its release, including test and disaster recovery systems.
- Find the PTF for your release in the table above, and order it from IBM Fix Central or through your usual PTF process.
- Apply the PTF and restart as the PTF cover letter requires.
- Check the PTF status with DSPPTF and record it.
- Limit access to IBM i network services to the hosts and users that need them.
Why it matters
CWE-367 is a time-of-check to time-of-use race. The system verifies a path, then uses it, and a symbolic link swapped in between can redirect the action to a protected object. IBM says an authenticated attacker could reach system objects this way.
Attack complexity is high because of the timing needed, yet scope is changed and all three impact ratings are high. Timing flaws are often shown to be practical once understood, so do not rely on difficulty. It shares a bulletin with CVE-2026-16908.
The weakness class here is CWE-367 (Time-of-check Time-of-use Race Condition). The NVD record scores it 8.5, which is high severity. IBM's bulletin gives the same score. The CVSS vector reads attack vector over the network, high attack complexity, low privileges required, no user interaction. Scope is changed, meaning the impact can reach beyond the vulnerable component. Impact on confidentiality, integrity and availability is rated high, high and high. The record's KEV flag is false, so this CVE is not in CISA's Known Exploited Vulnerabilities catalog, and the advisory I fetched does not report exploitation.
Safeguard's Gold directory tracks this CVE, and reachability analysis helps you decide which affected components matter most for your own software.
Quick check
Is a race condition realistic to exploit?
The record rates complexity as high, but races are often made reliable with effort. Patching is cheaper than depending on timing.
Sources
- IBM security bulletin
- Safeguard Gold entry for CVE-2026-16967, which summarizes the NVD record
Last reviewed: 18 October 2026.
