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CVE-2026-64055
net: ethernet: cortina: Carry over frag counter
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem drivers/net. Debian urgency: not yet assigned.
Debian does not build this code. The per-release build detail is under "Where it lives" below.
What to do, per Debian release
Debian's own status for CVE-2026-64055 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 | fixed | 6.1.176-1 | Update the kernel and reboot. Fixed in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The gmac_rx() NAPI poll function assembles packets in an SKB from a ring buffer. If the ring buffer gets completely emptied during a poll cycle, we exit gmac_rx(), but the packet is not yet completely assembled in the SKB, yet the fragment counter frag_nr is reset to zero on the next invocation. Solve this by making the RX fragment counter a part of the port struct, and carry it over between invocations. Reset the fragment counter only right after calling napi_gro_frags(), on error (after calling napi_free_frags()) or if stopping the port. Reset it in some place where not strictly necessary just to emphasize what is going on. This was found by Sashiko during normal patch review.
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.
drivers/net/ethernet/cortina/gemini.c
- What this is
- ARM/CORTINA SYSTEMS GEMINI ARM ARCHITECTUREMAINTAINERS section matched on drivers/net/ethernet/cortina/ · linux-arm-kernel@lists.infradead.org · Maintained
- Kernel module
- none to look for. The file would have gone into gemini, and Debian does not compile it into that module, so finding gemini in lsmod would say nothing about this CVE.
Check it on the machine
grep -wE 'CONFIG_ETHERNET|CONFIG_GEMINI_ETHERNET|CONFIG_NET_VENDOR_CORTINA' /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 does not build this code. In 4 releases below, every kernel flavour Debian publishes has the switch off, so the vulnerable file is compiled into no kernel binary Debian ships.
- bookworm, trixie, forky, sidn
- n
- not enabled on any flavour - this release does not build the code
- Build switches
- CONFIG_ETHERNET, CONFIG_GEMINI_ETHERNET, CONFIG_NET_VENDOR_CORTINA
- 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
- 2026-07-19 (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 42.5% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/net
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.16 | 5.10.258 | df31e3b64455 |
| 4.16 | 5.15.209 | 7af1fabdee74 |
| 4.16 | 6.1.175 | 75105fcf73f1 |
| 4.16 | 6.6.142 | 78cf08b3be47 |
| 4.16 | 6.12.92 | 7123cf481e21 |
| 4.16 | 6.18.34 | c373b34877af |
| 4.16 | 7.0.11 | 46806096f35b |
| 4.16 | 7.1 | ebd8ec2b309e |
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
- The bug is in the Cortina Gemini GMAC RX NAPI path (gmac_rx), which processes incoming Ethernet frames delivered by hardware DMA; a remote attacker on any routable network can send crafted multi-fragment frames to the device's NIC without local access.
- AC:LAttack complexity, low
- An attacker controls frame size (jumbo frames exceeding the 2048-byte RX buffer fragment size) and traffic timing to drain the RX ring mid-packet across NAPI poll cycles, reliably reproducing the lost frag_nr condition without depending on uncontrollable system state.
- PR:NPrivileges required, none
- Exploitation requires only the ability to send Ethernet frames to the target interface; no local account, kernel capability, or authentication on the victim system is needed.
- UI:NUser interaction, none
- Packet reception and NAPI processing are fully automatic; no victim user action such as mounting a filesystem or opening a file is required.
- S:UScope, unchanged
- The vulnerability corrupts kernel skb metadata in the network driver and affects only the kernel's own security domain; it does not cross a VM, container, or IOMMU boundary by itself.
- C:HConfidentiality impact, high
- Resetting frag_nr to zero while rx_skb retains prior fragments causes skb_fill_page_desc to overwrite fragment slot 0, shrinks nr_frags while inflating skb->len, and can trigger out-of-bounds kernel reads when GRO and the network stack process the corrupted skb.
- I:HIntegrity impact, high
- The bug corrupts kernel heap skb fragment metadata (overwritten page descriptors, inconsistent nr_frags versus len), which is memory corruption in kernel structures that can be leveraged for arbitrary write or control-flow hijack primitives.
- A:HAvailability impact, high
- Submitting a corrupted multi-fragment skb to napi_gro_frags and the upper network stack can cause kernel oops, BUG, or panic during fragment traversal, checksum, or GRO processing.