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CVE-2026-64355
bpf: Reject fragmented frames in devmap
Published 2026-07-25 (3 months ago) by the Linux kernel CNA. Subsystem kernel/bpf. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-64355 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-4720-1 · 2026-08-05 · text | 6.1.180-1 | Update the kernel and reboot. DLA-4720-1 shipped the fix on 2026-08-05, in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.96-1 | Update the kernel and reboot. Fixed in 6.12.96-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.4-1 | Update the kernel and reboot. Fixed in 7.1.4-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4724-1 · 2026-08-07 · text | 6.12.100-1~deb12u1 | Update the kernel and reboot. DLA-4724-1 shipped the fix on 2026-08-07, in 6.12.100-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Devmap broadcast redirects clone the packet for all but the last destination. For native XDP, that clone path copies only the linear xdp_frame data, while fragmented frames keep skb_shared_info in tailroom outside the linear area. Cloning such a frame leaves XDP_FLAGS_HAS_FRAGS set but without valid frag metadata, and the later free path can interpret uninitialized tail data as skb_shared_info, leading to an out-of-bounds access during frame return. Reject fragmented native XDP frames in dev_map_enqueue_clone(). Add the same restriction to the generic XDP clone path in dev_map_redirect_clone(). Generic XDP represents fragmented packets as nonlinear skbs, and rejecting them here keeps clone-based broadcast support aligned between native and generic XDP.
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.
kernel/bpf/devmap.c
- What this is
- XDP (eXpress Data Path)MAINTAINERS section matched on kernel/bpf/devmap.c · netdev@vger.kernel.org · Supported
Check it on the machine
grep -wE 'CONFIG_BPF|CONFIG_BPF_SYSCALL|CONFIG_NET' /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.
Show whether Debian builds this, per release
Debian builds this code. Every release below compiles the affected file into the kernels it ships.
- bookworm, trixie, forky, sid, bookworm · linux-6.12y
- y
- built into the kernel image on every flavour - only a patch removes it
- Build switches
- CONFIG_BPF, CONFIG_BPF_SYSCALL, CONFIG_NET
- Reads as
- all on means the file is compiled; any one off means it is not.
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
- 2026-07-25 (3 months ago)source
- CVSS
- 9.8 critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.51%, higher than 42.4% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- kernel/bpf
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.14 | 5.15.212 | 47baddc856ae |
| 5.14 | 6.1.178 | 07a4c11ee8ef |
| 5.14 | 6.6.145 | bccbab36ff22 |
| 5.14 | 6.12.96 | c5b4f5efcb55 |
| 5.14 | 6.18.39 | a9bb2d9c798c |
| 5.14 | 7.1.4 | 51d07c12ca41 |
| 5.14 | 7.2 | aa496720618f |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4724-1 | 2026-08-07 | bookworm 6.12.100-1~deb12u1 | tracker |
| DLA-4723-1 | 2026-08-07 | bullseye 6.1.180-1~deb11u1 | tracker |
| DLA-4720-1 | 2026-08-05 | bookworm 6.1.180-1 | 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:NAttack vector, network
- A remote peer can send an oversized packet that a fragment-capable NIC represents as a multi-buffer XDP frame, reaching the vulnerable devmap broadcast clone path on a configured forwarding host.
- AC:LAttack complexity, low
- No race or uncontrollable timing condition is required; fragmented packets reliably enter the faulty clone path and can be sent repeatedly.
- PR:NPrivileges required, none
- Although initial-namespace CAP_BPF and CAP_NET_ADMIN are needed to configure the XDP deployment, the attacker sending packets through the already-configured unauthenticated data path needs no privileges.
- UI:NUser interaction, none
- Packet reception and XDP processing occur automatically without victim action.
- S:UScope, unchanged
- The corruption compromises resources governed by the same host-kernel security authority and does not inherently cross a VM, IOMMU, or other distinct boundary.
- C:HConfidentiality impact, high
- Uninitialized fragment descriptors are consumed as page references and can be used by scatter-gather transmitters for unintended DMA mappings, potentially exposing arbitrary kernel memory.
- I:HIntegrity impact, high
- An uninitialized fragment count can overrun fixed-size driver arrays, while bogus page references can cause invalid refcount decrements, premature frees, and exploitable kernel memory corruption.
- A:HAvailability impact, high
- Invalid fragment metadata can fault during DMA mapping, transmission, or frame return and cause a kernel oops or panic; an attacker can trigger this repeatedly.