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CVE-2026-53247
net: ethernet: mtk_eth_soc: Fix use-after-free in metadata dst teardown
Published 2026-06-25 (4 months ago) by the Linux kernel CNA. Subsystem drivers/net. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-53247 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| 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 | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
mtk_free_dev() calls metadata_dst_free() which frees the metadata_dst with kfree() immediately, bypassing the RCU grace period. In the RX path, skb_dst_set_noref() sets a non-refcounted pointer from the skb to the metadata_dst. This function requires RCU read-side protection and the dst must remain valid until all RCU readers complete. Since metadata_dst_free() calls kfree() directly, a use-after-free can occur if any skb still holds a noref pointer to the dst when the driver tears it down. Replace metadata_dst_free() with dst_release() which properly goes through the refcount path: when the refcount drops to zero, it schedules the actual free via call_rcu_hurry(), ensuring all RCU readers have completed before the memory is freed.
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/mediatek/mtk_eth_soc.c
- What this is
- MEDIATEK ETHERNET DRIVERMAINTAINERS section matched on drivers/net/ethernet/mediatek/ · netdev@vger.kernel.org · Maintained
- Kernel module
- mtk_eth
Check it on the machine
grep -wE 'CONFIG_ETHERNET|CONFIG_NET_MEDIATEK_SOC|CONFIG_NET_VENDOR_MEDIATEK' /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 mtk_ethPrints 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 does not build this code in 1 release. It does build it in 3 releases, so the answer depends on which release the machine runs.
- bookwormn
- trixieMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/cloud-arm64, armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- forky, sidMnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt-amd64, arm64/cloud-arm64, armhf/armmp, armhf/armmp-lpae, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- n
- not enabled on any flavour - this release does not build the code
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_ETHERNET, CONFIG_NET_MEDIATEK_SOC, CONFIG_NET_VENDOR_MEDIATEK
- 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
- 2026-06-25 (4 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
- 0.69%, higher than 51.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- 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 |
|---|---|---|
| 6.2 | 6.6.143 | 72775977e89c |
| 6.2 | 6.12.94 | 459c6f35c58c |
| 6.2 | 6.18.36 | e634408d2b0c |
| 6.2 | 7.0.13 | 2d86aeb46d5f |
| 6.2 | 7.1 | 80df409e1a48 |
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
- Packets received on the affected MediaTek Ethernet/DSA data path can cause skbs to carry the vulnerable non-refcounted metadata dst. In a severe reasonable deployment, this is reachable by an unauthenticated network peer sending traffic to an exposed Ethernet interface.
- AC:LAttack complexity, low
- The RX path reliably assigns the metadata dst under the DSA hardware untagging conditions, and the bug is a straightforward lifetime violation during teardown. Given the requirement to choose higher severity when uncertain, the teardown timing does not justify AC:H.
- PR:NPrivileges required, none
- The attacker needs no credentials to send packets that enter the affected RX path and populate skbs with the stale metadata pointer. Administrative teardown is a device lifecycle condition, not an attacker privilege requirement.
- UI:NUser interaction, none
- No victim user must open a file or perform a protocol-level action for malicious packets to enter the vulnerable path. The vulnerable condition can occur during normal device teardown or cleanup.
- S:UScope, unchanged
- The corruption occurs within the same kernel security authority as the affected network driver and networking stack. There is no guest-to-host, IOMMU, or separate-scope boundary crossing.
- C:HConfidentiality impact, high
- This is a kernel use-after-free of a metadata_dst object referenced from skbs. Such memory corruption can plausibly be shaped into kernel memory disclosure.
- I:HIntegrity impact, high
- A kernel use-after-free can plausibly be exploited through heap reuse to corrupt controlled kernel objects or hijack control/data flow. Under the required higher-severity rule, integrity impact is High.
- A:HAvailability impact, high
- The stale dst pointer can be dereferenced by GRO/DSA/network stack processing after immediate kfree. Even without full exploitation, this can cause kernel oops or panic.