High [CVE-2026-98550] reject invalid and unexpected GRP_ACK_MSG to prevent bc_ackers underflow
This high-severity Red Hat Linux advisory covers CVE-2026-98550; related products: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9.
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Summary
reject invalid and unexpected GRP_ACK_MSG to prevent bc_ackers underflow. Red Hat rates this important (CVSS 7.5).
Weakness: CWE-191.
Affected products named by the advisory: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Red Hat OpenShift Container Platform 4; and 1 more.
Affected products named by the advisory: Red Hat package: kernel-rt.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · high-confidence parse· fetched 9 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists. Confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 9 days ago·verify at source
Mitigation checklist
- --- CME Mitigation Guidance (2026-10-20) --- Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure. The highest-value action is to enforce strict sequence verification and reject unexpected GRP_ACK_MSG messages in the TIPC kernel subsystem before decrementing bc_ackers: upgrade to the fixed Kernel/Kernel Ivos Qualcomm/Kernel Rt/Openshift/Ose Rhel Coreos/Kpatch builds, which drop GRP_ACK_MSG immediately if grp->bc_ackers is zero, require acked to strictly equal grp->bc_snd_nxt, and reject duplicate acknowledgments, closing all 2 injection vectors (unexpected GRP_ACK_MSG when bc_ackers is zero, stale sequence ACK injection exploiting the sequence gap in active broadcast rounds). Until patched, this is only a concern on Linux systems running the TIPC kernel module with active or listening group communication sockets — Non-Linux platforms are unaffected — so Restrict network connectivity capable of delivering TIPC traffic to target nodes and avoid loading the TIPC kernel module where group sockets are not needed. As a compensating measure, Enable compiler integer overflow and conversion checks or UBSan integer sanitization to trap runtime unsigned integer underflows when bc_ackers is decremented below zero. These controls limit blast radius and contain exploitation, but they do not fix the underlying TIPC acknowledgment integer underflow defect — apply the upstream patch to fully remediate. Highest-impact CME: CME-119 Compiler Integer Overflow and Conversion Safety (-ftrapv / UBSan Integer) (medium)
Official advisory · high-confidence parse· fetched 9 days ago·verify at source
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