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CVE-2026-80994
net: openvswitch: fix flow mask use-after-free on flow deletion
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem net/openvswitch. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-80994 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
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.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
net/openvswitch/datapath.c
- What this is
- OPENVSWITCHMAINTAINERS section matched on net/openvswitch/ · netdev@vger.kernel.org · Maintained
- Kernel module
- openvswitch
Check it on the machine
grep -w CONFIG_OPENVSWITCH /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w openvswitchPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this as a loadable module. Every release below compiles it as a module on every flavour, so whether the code is in the running kernel depends on whether that module is loaded.
- bookworm, trixie, forky, sid, bookworm · linux-6.12m
- m
- a loadable module on every flavour - check lsmod, can be blacklisted
- Build switch
- CONFIG_OPENVSWITCH
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-09-11 (37 days ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 6.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/openvswitch
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 3.16 | 5.10.270 | ea5f7b45b582 |
| 3.16 | 5.15.221 | 18ce1a8b7499 |
| 3.16 | 6.1.188 | c15ef9a5bf59 |
| 3.16 | 6.6.157 | 64051fe200c7 |
| 3.16 | 6.12.109 | 0ba5cbc2f049 |
| 3.16 | 6.18.50 | ac73e3af571d |
| 3.16 | 7.2.4 | 7f072b84afd0 |
| 3.16 | 7.3 | 4e30317ff67a |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The UAF is reached only through OVS_FLOW_CMD_DEL on the ovs_flow Generic Netlink family via a local sendmsg() on an AF_NETLINK socket; packet receive and remote protocols cannot delete flows or call ovs_flow_cmd_del().
- AC:LAttack complexity, low
- The attacker owns unique-mask flow insert and CMD_DEL with NLM_F_ECHO; after ovs_unlock(), GFP_KERNEL genlmsg_new() can sleep under attacker-induced memory pressure until kfree_rcu() of sw_flow_mask completes, so the race is attacker-controlled and repeatable.
- PR:LPrivileges required, low
- OVS_FLOW_CMD_DEL/NEW and OVS_DP_CMD_NEW use GENL_UNS_ADMIN_PERM with netnsok, so only CAP_NET_ADMIN in the socket user namespace is required; an unprivileged user obtains that via unshare -Urn, and MODULE_ALIAS_GENL_FAMILY autoloads openvswitch.ko.
- UI:NUser interaction, none
- The attacker creates the datapath, installs a unique-mask flow, and deletes it with NLM_F_ECHO from their own process; no victim action is required.
- S:UScope, unchanged
- The slab use-after-free of sw_flow_mask stays in kernel heap on the same host and does not cross a VM, IOMMU, or hypervisor boundary.
- C:HConfidentiality impact, high
- ovs_nla_put_mask() reads the freed flow->mask->key and copies it into the CMD_DEL netlink reply delivered to the attacker, so a reused or heap-sprayed slab object becomes an arbitrary kernel-memory disclosure primitive.
- I:HIntegrity impact, high
- This is a slab use-after-free of sw_flow_mask; after kfree_rcu() the attacker can reclaim the object so fill-info interprets attacker-controlled bytes as a flow mask, enabling heap spraying and write/control-flow primitives.
- A:HAvailability impact, high
- KASAN reports a slab-use-after-free in __ovs_nla_put_key during ovs_flow_cmd_del, and dereference of the freed mask can oops or panic the kernel; the attacker can repeat CMD_DEL to deny availability.