CVE-2026-16826 is a medium severity (CVSS 5.3) OS command injection flaw in IBM i 7.3, 7.4, 7.5 and 7.6. A local attacker could execute arbitrary commands. IBM provides a PTF for each release under licensed program 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: SJ11305
- IBM i 7.5: SJ11306
- IBM i 7.4: SJ11307
- IBM i 7.3: SJ11308
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-78 means a command is built from input without neutralizing special elements. IBM says a local attacker could execute arbitrary commands. The vector needs local access and low privileges, and rates confidentiality, integrity and availability impact low.
The same bulletin lists several other IBM i issues, mostly low to medium. Because PTFs are the normal vehicle, apply this one in the same window as others you already plan. Local-only flaws are less urgent than network ones, but on shared IBM i partitions with many user profiles they still count.
The weakness class here is CWE-78 (OS Command Injection). The NVD record scores it 5.3, which is medium severity. IBM's bulletin gives the same score. The CVSS vector reads attack vector with local access, low attack complexity, low privileges required, no user interaction. Scope is unchanged. Impact on confidentiality, integrity and availability is rated low, low and low. 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
Why is the score only 5.3 for command execution?
The record rates each impact as low and requires local access with low privileges, so the potential damage is bounded.
Sources
- IBM security bulletin
- Safeguard Gold entry for CVE-2026-16826, which summarizes the NVD record
Last reviewed: 18 October 2026.
