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CVE-2026-89487
openvswitch: only skb_tx_error() a packet we are about to drop
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-2026-89487 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
queue_userspace_packet() borrows the packet skb -- it only copies it into a private netlink message (user_skb) and does not own it; on return do_execute_actions() keeps forwarding it through the flow's remaining actions. Its error path nevertheless calls skb_tx_error(skb), which via skb_zcopy_clear() does skb_shinfo(skb)->flags &= ~SKBFL_ALL_ZEROCOPY, stripping SKBFL_SHARED_FRAG from that live skb (skb_tx_error()'s kerneldoc says "skb must be freed afterwards"). For a MSG_ZEROCOPY skb carrying page-cache frags, SKBFL_SHARED_FRAG is what makes esp_input() skb_cow_data() before in-place AEAD; once it is stripped a later local ESP-in-UDP delivery decrypts in place over pages the sender does not own -- an unprivileged page-cache write (the "Fragnesia" primitive). do_execute_actions() ignores output_userspace()'s return value, so any action after a failed USERSPACE upcall inherits the stripped skb. Move the skb_tx_error() to the flow-miss drop path - the "default" branch of ovs_dp_process_packet()'s switch(error), before kfree_skb(). The call has been here since commit 36d5fe6a0007 ("core, nfqueue, openvswitch: Orphan frags in skb_zerocopy and handle errors") but was harmless until esp_input() began relying on SKBFL_SHARED_FRAG to gate in-place decrypt; only then did stripping it on a still-forwarded skb become a page-cache write primitive.
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
- 0.13%, higher than 2.3% 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 |
|---|---|---|
| 3.14 | 5.10.270 | 5de5d554141a |
| 3.14 | 5.15.221 | 48db11e115d1 |
| 3.14 | 6.1.188 | 4477222e2916 |
| 3.14 | 6.6.157 | 4d5c460ef875 |
| 3.14 | 6.12.109 | 6767d70cf46f |
| 3.14 | 6.18.50 | e41a59fc056f |
| 3.14 | 7.2.4 | 5d85eef222cf |
| 3.14 | 7.3 | 0dbc2398fca3 |
| 3.10.51 | 0 | 0 |
| 3.12.40 | 0 | 0 |
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 strip runs only on a locally originated MSG_ZEROCOPY skb that still has a zerocopy uarg (skb_zcopy_clear is a no-op otherwise); NIC-received packets never carry that uarg, and the later in-place ESP decrypt is via a local SA, so a local account is required.
- AC:LAttack complexity, low
- The attacker fully controls the OVS flow (non-last USERSPACE with a PID that makes genlmsg_unicast fail), the MSG_ZEROCOPY send, and the ESP SA/payload; do_execute_actions() ignores the upcall error, so the shared-frag strip and in-place decrypt are deterministic with no race beyond attacker influence.
- PR:LPrivileges required, low
- OVS genetlink families are netnsok and use GENL_UNS_ADMIN_PERM (CAP_NET_ADMIN in the socket user_ns); an unprivileged user can unshare -Urn, create a datapath/flow, enable SO_ZEROCOPY, and install xfrm SAs, while the global page cache remains the corruption target.
- UI:NUser interaction, none
- The attacker installs the OVS userspace-then-output flow, sends the MSG_ZEROCOPY packet, and completes local ESP-in-UDP delivery without any victim action such as opening a file or mounting a filesystem.
- S:UScope, unchanged
- The resulting page-cache write is a standard in-kernel memory-corruption/privilege-escalation primitive on the same host; it does not cross a VM hypervisor or IOMMU security boundary.
- C:HConfidentiality impact, high
- Clearing SKBFL_SHARED_FRAG lets later esp_input() skip skb_cow_data() and AEAD-decrypt in place over page-cache-backed frags, a write primitive into globally cached file/code pages that can be leveraged for arbitrary disclosure.
- I:HIntegrity impact, high
- With the shared-frag marker stripped, ESP decrypts attacker-controlled plaintext in place over page-cache pages the sender does not own, yielding the Fragnesia unprivileged write into files the attacker could only read.
- A:HAvailability impact, high
- In-place writes into page-cache-backed or still-mapped zerocopy pages corrupt shared kernel/file state and readily cause oopses, panics, and process crashes; skb_tx_error also completes the uarg while the skb is still in flight.