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CVE-2026-74545
rtase: fix double free of multi-frag skb on DMA map failure
Published 2026-08-15 (2 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-2026-74545 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 | 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 | 7.1.8-1 | Update the kernel and reboot. Fixed in 7.1.8-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.8-1 | Update the kernel and reboot. Fixed in 7.1.8-1. 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
In rtase_start_xmit(), when the head buffer DMA mapping fails after rtase_xmit_frags() has mapped all fragments, the error path clears the fragment descriptors with rtase_tx_clear_range(), which frees the skb through the last-frag slot and accounts tx_dropped. Control then falls through to the common error label, which frees the same skb a second time and counts it again. Return right after clearing the fragments when the skb owns frags; the no-frag case still drops through and frees the head skb once.
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/realtek/rtase/rtase_main.c
- What this is
- RTASE ETHERNET DRIVERMAINTAINERS section matched on drivers/net/ethernet/realtek/rtase/ · netdev@vger.kernel.org · Maintained
Check it on the machine
grep -wE 'CONFIG_ETHERNET|CONFIG_NET_VENDOR_REALTEK|CONFIG_RTASE' /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. The build rule could not be established for 1 release, so nothing is claimed about those.
- bookworm?
- trixie, forky, sid, bookworm · linux-6.12n
- ?
- not established - no Makefile entry for the affected file
- n
- not enabled on any flavour - this release does not build the code
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switches
- CONFIG_ETHERNET, CONFIG_NET_VENDOR_REALTEK, CONFIG_RTASE
- 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
- 2026-08-15 (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
- 0.67%, higher than 51.1% 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 |
|---|---|---|
| 6.12 | 6.12.103 | 4f09172aff5f |
| 6.12 | 6.18.44 | db986098f308 |
| 6.12 | 7.1.8 | de691dc3227b |
| 6.12 | 7.2 | 6fb7b769d6ed |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | 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
- The flaw is in rtase_start_xmit (ndo_start_xmit) on the Realtek Automotive Switch PCIe netdev; a remote peer can reach it by sending traffic that the host forwards, bridges, or answers out the rtase interface on automotive gateways and industrial routers without local shell access.
- AC:LAttack complexity, low
- NETIF_F_SG enables multi-fragment TX skbs that rtase_xmit_frags maps before the head; an attacker can reliably create such packets and pressure SWIOTLB/IOVA resources with concurrent egress so the final head dma_map_single fails after fragment mapping succeeds, deterministically hitting the buggy error path.
- PR:NPrivileges required, none
- Exploitation needs only the ability to inject or induce network traffic transmitted via the rtase netdev; no target credentials, capabilities, or local account are required on forwarding automotive/industrial gateways where this driver is deployed.
- UI:NUser interaction, none
- No victim interaction is required; the double free occurs automatically when the kernel queues a multi-fragment skb and the head DMA mapping fails during normal transmit error handling.
- S:UScope, unchanged
- The double free corrupts kernel heap allocator state on the host running the rtase driver; it does not cross VM, container, or IOMMU security boundaries.
- C:HConfidentiality impact, high
- Double-freeing the same skb is kernel heap memory corruption that can corrupt freelist metadata and enable reuse of freed skb memory for arbitrary kernel memory disclosure, not merely a bounded leak.
- I:HIntegrity impact, high
- Heap corruption from freeing the same skb twice can be shaped into arbitrary kernel memory writes or control-flow hijacking via slab reuse, not limited to dropping a single packet.
- A:HAvailability impact, high
- Double-freeing an skb reliably corrupts the slab allocator and can trigger immediate oops, panic, or watchdog reset; the attacker can repeat multi-fragment transmits under DMA pressure for sustained denial of service on safety-critical automotive networks.