Copyright © 2012 Red Hat, Inc. All rights reserved. Important 2026-07-27T00:00:00 kernel: net: openvswitch: reject oversized nested action attrs 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H CWE-130

In the Linux kernel, the following vulnerability has been resolved: net: openvswitch: reject oversized nested action attrs Open vSwitch stores generated flow actions as nlattrs, whose nla_len field is u16. Commit a1e64addf3ff ("net: openvswitch: remove misbehaving actions length check") allowed the total sw_flow_actions stream to grow beyond 64 KiB, which is valid, but also removed the last guard preventing a generated nested action attribute from exceeding U16_MAX. An oversized generated container can thus be closed with a truncated nla_len. A later dump or teardown then walks a structurally different stream than the one that was validated. In particular, an oversized nested CLONE/CT action may cause subsequent bytes in the generated stream to be interpreted as independent actions. Keep the larger total-action-stream behavior, but make nested action close reject generated containers that do not fit in nla_len, and return the error through all callers. For recursive SAMPLE, CLONE, DEC_TTL, and CHECK_PKT_LEN builders, trim resource-owning action-list tails in reverse construction order before discarding failed wrappers, so resources copied into the rejected tails are released before the wrappers are removed. Most failed outer wrappers are discarded by truncating actions_len after child resources have been released. CHECK_PKT_LEN also trims its parent after branch resources are gone. SET/TUNNEL close failures unwind their known tun_dst ownership directly, and SET_TO_MASKED has no external ownership and truncates on close failure.

A flaw was found in Open vSwitch in the Linux kernel. Improper handling of oversized nested action attributes can lead to a truncated length field, which could be exploited by a local attacker to alter kernel memory. This alteration might result in the disclosure of sensitive information or a local privilege escalation (LPE).

Note that Red Hat Enterprise Linux 9.6 and layered products which include the 9.6 kernel do not contain the commits that introduced this vulnerability. Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 2026-08-07T00:00:00Z RHSA-2026:51603 kernel-0:5.14.0-284.186.1.el9_2 Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 2026-08-07T00:00:00Z RHSA-2026:51604 kernel-rt-0:5.14.0-284.186.1.rt14.471.el9_2 Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions 2026-08-07T00:00:00Z RHSA-2026:51746 kernel-0:5.14.0-427.143.1.el9_4 Red Hat Enterprise Linux 10 Affected kernel Red Hat Enterprise Linux 6 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel-rt Red Hat Enterprise Linux 8 Not affected kernel Red Hat Enterprise Linux 8 Not affected kernel-rt Red Hat Enterprise Linux 9 Affected kernel Red Hat Enterprise Linux 9 Affected kernel-rt Red Hat OpenShift Container Platform 4 Affected rhcos https://www.cve.org/CVERecord?id=CVE-2026-64531 https://nvd.nist.gov/vuln/detail/CVE-2026-64531 https://lore.kernel.org/linux-cve-announce/2026072732-CVE-2026-64531-e4ce@gregkh/T