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CVE-2026-74616
xdp: reject clones that overrun skb_shared_info tailroom
Published 2026-08-22 (2 months ago) by the Linux kernel CNA. Subsystem net/core. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-74616 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
xdpf_clone() clones broadcast copies into a single page and sets frame_sz to PAGE_SIZE. __xdp_build_skb_from_frame() later treats that page like a normal XDP frame and expects the usual skb_shared_info tailroom at the end of the buffer. The current check only rejects frames whose linear xdp_frame header, headroom, and packet data exceed PAGE_SIZE. A source frame backed by a larger allocation can still satisfy that check while extending into the clone's required shared-info area. When such a clone is converted back into an skb, build_skb_around() places skb_shared_info over live packet bytes and later writes can corrupt XDP return metadata. Reject clones unless their linear area fits inside SKB_WITH_OVERHEAD(PAGE_SIZE), matching the tailroom requirement already enforced by the XDP-to-skb conversion path.
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/core/xdp.c
- What this is
- XDP (eXpress Data Path)MAINTAINERS section matched on net/core/xdp.c · netdev@vger.kernel.org · Supported
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
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 Debian linux-config packages
Signals
- Published
- 2026-08-22 (2 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
- net/core
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.14 | 5.15.216 | 58408982fa39 |
| 5.14 | 6.1.183 | 685edea27ac6 |
| 5.14 | 6.6.152 | ba13763d667e |
| 5.14 | 6.12.104 | ef4b7c7046d2 |
| 5.14 | 6.18.45 | fab820f1691a |
| 5.14 | 7.1.9 | f463b6f4957c |
| 5.14 | 7.2 | e48e8edbef2e |
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:NAttack vector, network
- Remote packets on an XDP ingress netdev whose program calls bpf_xdp_redirect_map() with BPF_F_BROADCAST reach xdpf_clone() through dev_map_enqueue_multi(); edge L4 load balancers and container fan-out to veth peers are common deployments where cloned frames later hit __xdp_build_skb_from_frame() without any local attacker access.
- AC:LAttack complexity, low
- Once broadcast devmap redirect is deployed, an attacker can reliably craft linear frames whose headroom plus payload fall in the SKB_WITH_OVERHEAD(PAGE_SIZE)..PAGE_SIZE window; no race, timing luck, or uncontrollable memory layout is required and the condition can be retried with each packet.
- PR:NPrivileges required, none
- Loading/attaching the XDP program and populating the devmap requires CAP_BPF and CAP_NET_ADMIN on the host, but an unauthenticated remote sender on the already-configured datapath needs no privileges on the victim system, matching the CNA pattern used for the related devmap broadcast clone issue CVE-2026-64355.
- UI:NUser interaction, none
- Exploitation is driven entirely by network traffic processed in NAPI/softirq after XDP redirect; no victim mount, file open, or other interactive action is required beyond packets reaching the configured interface.
- S:UScope, unchanged
- The flaw corrupts skb_shared_info placement and metadata within the host kernel address space during skb construction; it does not inherently cross VM, hypervisor, or IOMMU security boundaries.
- C:HConfidentiality impact, high
- build_skb_around() places skb_shared_info over live packet bytes and memset initializes it there; subsequent skb/shinfo access can read kernel metadata and adjacent buffer contents beyond intended bounds, constituting exploitable out-of-bounds memory disclosure.
- I:HIntegrity impact, high
- Overlapping skb_shared_info tailroom lets kernel writes corrupt packet data and lets attacker-influenced bytes corrupt shinfo fields used by later stack, GRO, and transmit paths, giving an out-of-bounds write primitive over frame metadata.
- A:HAvailability impact, high
- Tailroom overlap during __xdp_build_skb_from_frame() can fault or corrupt state during skb construction and downstream processing, producing kernel oops/panic; an attacker can trigger this repeatedly with crafted packets on the broadcast redirect path.