CVE-2026-4942
MEDIUMCVE-2026-4942 is a medium-severity (CVSS 5.9) CWE-757 vulnerability in ibm i. O3 Security detects and blocks CVE-2026-4942 exploitation at runtime via eBPF exploit-chain detection and L7 egress monitoring, even on unpatched systems.
IBM i 7.6, 7.5, 7.4, and 7.3 could allow a remote attacker to send a specifically crafted message and downgrade the Transport Layer Security (TLS) protocol to a version disabled in…
Description
IBM i 7.6, 7.5, 7.4, and 7.3 could allow a remote attacker to send a specifically crafted message and downgrade the Transport Layer Security (TLS) protocol to a version disabled in the server configuration.
Affected Products
iibmDetection & mitigation playbook
Vendor / applianceDetect
Inventory every ibm i deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for exploitation at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.
Remediation status
No patch has shipped for CVE-2026-4942 yet — track the ibm i advisory for a fixed release and apply the workarounds below in the meantime.
Mitigate without a patch
Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.
How O3 protects you
O3 detects and blocks CVE-2026-4942 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.
Tailored to CVE-2026-4942. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-4942 being exploited in your environment?
O3's eBPF runtime sensors and L7 egress monitoring detect and block the CVE-2026-4942 exploit chain at execution — protecting unpatched and end-of-life systems until the vendor patch is applied.