CVE-2026-80994

net: openvswitch: fix flow mask use-after-free on flow deletion

State: Published
Severity: 7.8 High
Published: Sep 11, 2026
Updated: Oct 19, 2026
Reserved: Aug 26, 2026

Description

In the Linux kernel, the following vulnerability has been resolved:

net: openvswitch: fix flow mask use-after-free on flow deletion

The commit in the Fixes tag below made so flow->mask free is scheduled via RCU right after it is removed from the flow table. The pointer stays in the flow structure and it can be accessible while in the same RCU critical section. This is done to avoid requiring ovs_mutex for the ovs_flow_free().

However, while removing the flow during processing of CMD_DEL, we do not take RCU read lock before the removal, and ovs_flow_cmd_fill_info() uses the flow->mask pointer afterwards. The RCU read lock is taken, but it's already late at that point. The comment on that line acknowledges that the lock is cosmetic and doesn't serve a real purpose.

This leads to use-after-free if the RCU grace period passes between removal and the filling. It is a short race window, but it is there and can lead to a real crash in case memory allocation for the info takes a bit longer:

BUG: KASAN: slab-use-after-free in __ovs_nla_put_key net/openvswitch/flow_netlink.c:1996 BUG: KASAN: slab-use-after-free in ovs_nla_put_key+0x2463/0x2e30 net/openvswitch/flow_netlink.c:2250 Read of size 4 at addr ffff88801ee89970 by task ovs_flow_del_ec/9487

Call Trace: <TASK> __ovs_nla_put_key net/openvswitch/flow_netlink.c:1996 ovs_nla_put_key+0x2463/0x2e30 net/openvswitch/flow_netlink.c:2250 ovs_flow_cmd_fill_info+0x420/0x9c0 net/openvswitch/datapath.c:930 ovs_flow_cmd_del+0x53a/0x970 net/openvswitch/datapath.c:1467 ... netlink_rcv_skb+0x156/0x420 net/netlink/af_netlink.c:2556 </TASK>

Allocated by task 9487: mask_alloc net/openvswitch/flow_table.c:967 flow_mask_insert net/openvswitch/flow_table.c:1012 ovs_flow_tbl_insert+0xea2/0x1a90 net/openvswitch/flow_table.c:1084 ovs_flow_cmd_new+0x7e3/0xd90 net/openvswitch/datapath.c:1086 ... netlink_rcv_skb+0x156/0x420 net/netlink/af_netlink.c:2556

Freed by task 9485: rcu_free_sheaf+0x1e/0x100 mm/slub.c:5978 rcu_do_batch kernel/rcu/tree.c:2645 rcu_core+0x59c/0x10c0 kernel/rcu/tree.c:2897 handle_softirqs+0x1e4/0x9a0 kernel/softirq.c:622 ... instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062

ovs_flow_tbl_remove() must be called after the ovs_flow_cmd_fill_info() to avoid this race. This also helps with cleaning up the forced cast and the cosmetic RCU read lock. Before the commit in the Fixes tag the order did not matter as long as the flow object itself was not freed.

A wider RCU critical section could be another option, but we have a GFP_KERNEL allocation in the way.

Reported by Trend Micro's Zero Day Initiative as ZDI-CAN-32042.

Scores

CVSS	Score	Vector	Source
3.1	7.8 High	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H	Linux

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	56c19868e115fcf8d62d843e1b9616bb9837d0db to before ea5f7b45b582665541ddfb77dce98611354af4abAffected 56c19868e115fcf8d62d843e1b9616bb9837d0db to before 18ce1a8b7499c016d4a893d9b1db80608f73745dAffected 56c19868e115fcf8d62d843e1b9616bb9837d0db to before c15ef9a5bf594f93a31de2ec2ec394e2a903519aAffected 56c19868e115fcf8d62d843e1b9616bb9837d0db to before 64051fe200c7c759af71634bd2123552eaabb69aAffected 56c19868e115fcf8d62d843e1b9616bb9837d0db to before 0ba5cbc2f049af94ec94ff6f64958545efc5eaa2Affected 56c19868e115fcf8d62d843e1b9616bb9837d0db to before ac73e3af571da06c1d1cfe3f0f00dc978b851700Affected 56c19868e115fcf8d62d843e1b9616bb9837d0db to before 7f072b84afd05a77963eb1872f7174e280661dceAffected 56c19868e115fcf8d62d843e1b9616bb9837d0db to before 4e30317ff67a2eb12b4d890d39f72fd7e7117d48Affected
LinuxLinux	3.16Affected before 3.16Not affected 5.10.270 through 5.10.Not affected 5.15.221 through 5.15.Not affected 6.1.188 through 6.1.Not affected 6.6.157 through 6.6.Not affected 6.12.109 through 6.12.Not affected 6.18.50 through 6.18.Not affected 7.2.4 through 7.2.*Not affected 7.3 and laterNot affected

Product

Versions

LinuxLinux

56c19868e115fcf8d62d843e1b9616bb9837d0db to before ea5f7b45b582665541ddfb77dce98611354af4abAffected
56c19868e115fcf8d62d843e1b9616bb9837d0db to before 18ce1a8b7499c016d4a893d9b1db80608f73745dAffected
56c19868e115fcf8d62d843e1b9616bb9837d0db to before c15ef9a5bf594f93a31de2ec2ec394e2a903519aAffected
56c19868e115fcf8d62d843e1b9616bb9837d0db to before 64051fe200c7c759af71634bd2123552eaabb69aAffected
56c19868e115fcf8d62d843e1b9616bb9837d0db to before 0ba5cbc2f049af94ec94ff6f64958545efc5eaa2Affected
56c19868e115fcf8d62d843e1b9616bb9837d0db to before ac73e3af571da06c1d1cfe3f0f00dc978b851700Affected
56c19868e115fcf8d62d843e1b9616bb9837d0db to before 7f072b84afd05a77963eb1872f7174e280661dceAffected
56c19868e115fcf8d62d843e1b9616bb9837d0db to before 4e30317ff67a2eb12b4d890d39f72fd7e7117d48Affected

LinuxLinux

3.16Affected
before 3.16Not affected
5.10.270 through 5.10.*Not affected
5.15.221 through 5.15.*Not affected
6.1.188 through 6.1.*Not affected
6.6.157 through 6.6.*Not affected
6.12.109 through 6.12.*Not affected
6.18.50 through 6.18.*Not affected
7.2.4 through 7.2.*Not affected
7.3 and laterNot affected

References

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