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CVE-2026-98251
openvswitch: avoid reallocating confirmed conntrack labels
Published 2026-10-06 (13 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-2026-98251 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-6568-1 · 2026-10-16 · text | 6.12.113-1 | Update the kernel and reboot. DSA-6568-1 shipped the fix on 2026-10-16, in 6.12.113-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.8-1 | Update the kernel and reboot. Fixed in 7.2.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.8-1 | Update the kernel and reboot. Fixed in 7.2.8-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
ovs_ct_get_conn_labels() adds the labels extension when a conntrack entry does not have one. Confirmed conntracks can be read locklessly, so adding an extension may reallocate and free the extension block while another CPU accesses it. Only add the extension for unconfirmed conntracks. A confirmed conntrack without labels now fails the caller's label operation instead of reallocating its extension storage.
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/conntrack.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, sidm
- 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
- 2026-10-06 (13 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
- 0.14%, higher than 2.9% 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 |
|---|---|---|
| 4.3 | 5.10.271 | 4371d79ea744 |
| 4.3 | 5.15.222 | 7ff688aceada |
| 4.3 | 6.1.189 | 05eab8dced6b |
| 4.3 | 6.6.158 | 579d87ec1e1e |
| 4.3 | 6.12.112 | 2e6dd889c325 |
| 4.3 | 6.18.54 | d16f089bd700 |
| 4.3 | 7.2.8 | 8c9fcc6c3395 |
| 4.3 | 7.3 | 3f118c8217c1 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DSA-6568-1 | 2026-10-16 | trixie 6.12.113-1 | 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 bad state is created by local setup over the OVS genetlink datapath/flow commands: a ct(commit,labels) action hits ovs_ct_commit()->ovs_ct_set_labels()->ovs_ct_get_conn_labels() on a confirmed conntrack created before labels_used was raised. Packets only trigger it; the cause is local flow and conntrack ordering.
- AC:LAttack complexity, low
- The attacker creates the unlabelled confirmed conntrack (netfilter traffic before OVS init), installs the label flow, and sends both the triggering packet and the concurrent lockless ct->ext readers on other CPUs, so they control both sides of the krealloc race.
- PR:LPrivileges required, low
- The OVS datapath/flow genl ops use GENL_UNS_ADMIN_PERM, so CAP_NET_ADMIN in a user-owned network namespace (unshare -Urn) is enough; real root is not needed.
- UI:NUser interaction, none
- No victim action is needed; the attacker sets up the flows and sends all the packets themselves.
- S:UScope, unchanged
- The corruption is in the kernel's own conntrack extension memory and the impact stays inside the kernel's authority; no VM or hardware boundary is crossed.
- C:HConfidentiality impact, high
- nf_ct_ext_add() on a confirmed ct does krealloc(ct->ext) and frees the old extension block while other CPUs still dereference it locklessly. That is a slab use-after-free which can be reclaimed with attacker-sprayed data to leak kernel memory.
- I:HIntegrity impact, high
- Concurrent writers into the freed nf_ct_ext (labels, acct, ecache, helper data) write into reclaimed memory, a use-after-free write primitive that can be groomed to corrupt kernel objects.
- A:HAvailability impact, high
- The use-after-free on ct->ext can oops the kernel, and WARN_ON(nf_ct_is_confirmed(ct)) in nf_ct_ext_add() panics hosts with panic_on_warn set.