Look up another CVE · open CVE-2026-74701 in the interactive tracker
CVE-2026-74701
net/openvswitch: check Ethernet header length in key_extract()
Published 2026-08-22 (2 months 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-2026-74701 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-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6466-1 · 2026-08-25 · text | 6.12.105-1 | Update the kernel and reboot. DSA-6466-1 shipped the fix on 2026-08-25, in 6.12.105-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
When a packet arrives on an ARPHRD_NONE device (e.g. TUN), ovs_flow_key_extract() trusts the user-provided skb->protocol field: if it is ETH_P_TEB, the packet is classified as MAC_PROTO_ETHERNET and key_extract() is called without ensuring the skb has ETH_HLEN (14) bytes of linear data. key_extract() unconditionally pulls 2 * ETH_ALEN bytes for MAC addresses and parse_ethertype() pulls 2 more, either of which triggers a kernel BUG in __skb_pull() when the linear area is too small. kernel BUG at include/linux/skbuff.h:2848! RIP: 0010:key_extract+0xa7e/0xd90 net/openvswitch/flow.c:933 ovs_flow_key_extract+0x419/0xa70 ovs_vport_receive+0x222/0x390 netdev_frame_hook+0x3e0/0x630 tun_get_user+0x2d0c/0x38e0 Fixed by calling check_header() in key_extract() before accessing the Ethernet header.
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/flow.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
- 2026-08-22 (2 months 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 |
|---|---|---|
| 4.10 | 5.10.265 | e85278afd489 |
| 4.10 | 5.15.216 | 81f9b09f0ea3 |
| 4.10 | 6.1.183 | 831471718f6e |
| 4.10 | 6.6.152 | d8bea341b183 |
| 4.10 | 6.12.104 | 0b60b55652ba |
| 4.10 | 6.18.45 | a8139285c892 |
| 4.10 | 7.1.9 | 9b8cfbb58b85 |
| 4.10 | 7.2 | cf6f8b29befb |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DSA-6466-1 | 2026-08-25 | trixie 6.12.105-1 | 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 crash is reached when a crafted skb is processed in ovs_flow_key_extract() via ovs_vport_receive(); the documented reproducer injects it through tun_get_user() (write to a TUN fd), and the alternate path is OVS_PACKET_CMD_EXECUTE netlink—both require local syscall access, not remote packet delivery.
- AC:LAttack complexity, low
- The attacker fully controls skb length, skb->protocol (ETH_P_TEB), and linear versus fragmented layout; sending a sub-14-byte payload with ETH_P_TEB on an ARPHRD_NONE OVS port deterministically reaches key_extract() and triggers __skb_pull() BUG() without races or special heap layout.
- PR:LPrivileges required, low
- Attaching an ARPHRD_NONE netdev to an OVS datapath and using OVS_PACKET_CMD_EXECUTE require CAP_NET_ADMIN (GENL_UNS_ADMIN_PERM, netnsok); CAP_NET_ADMIN is obtainable inside an unprivileged user+network namespace, and TUN injection likewise requires CAP_NET_ADMIN or a TUN fd granted by a privileged setup.
- UI:NUser interaction, none
- No victim interaction is required; once OVS bridges an ARPHRD_NONE port (e.g. TUN), the attacker triggers the bug by injecting a single malformed packet via write() or netlink without any other user action.
- S:UScope, unchanged
- Impact is a kernel BUG/panic in the same kernel security authority as the attacker; this is not a VM escape, IOMMU bypass, or cross-namespace privilege boundary crossing.
- C:HConfidentiality impact, high
- Before the BUG, key_extract() calls ether_addr_copy() and parse_ethertype() on skb->data without validating ETH_HLEN, performing out-of-bounds reads of kernel skb buffer memory beyond the actual packet payload.
- I:HIntegrity impact, high
- Unchecked __skb_pull() on an undersized skb corrupts skb->data and skb->len metadata; this memory corruption of kernel packet state can be leveraged for further integrity violations beyond a simple controlled crash.
- A:HAvailability impact, high
- The flaw triggers kernel BUG() at __skb_pull() in include/linux/skbuff.h, producing a kernel oops/panic and denying all system availability on affected hosts running Open vSwitch with ARPHRD_NONE ports.