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CVE-2026-74435
rxrpc: rxrpc_verify_data ensure rx_dec_buffer alloc
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem net/rxrpc. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-74435 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 | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
rxrpc_recvmsg_data() calls rxrpc_verify_data() whenever the rxrpc_call.rx_dec_buffer is unallocated and assumes that upon successful return that rx_dec_buffer must be allocated. However, rxrpc_verify_data() does not request an allocation if the rxrpc_skb_priv.len is zero. In addition, failure to allocate rx_dec_buffer will result in a call to skb_copy_bits() with a NULL destination which can trigger a NULL pointer dereference. To prevent these issues rxrpc_verify_data() is modified to always attempt to allocate the rxrpc_call.rx_dec_buffer if it is NULL. This issue was identified with assistance of a private sashiko instance.
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/rxrpc/recvmsg.c
- What this is
- RXRPC SOCKETS (AF_RXRPC)MAINTAINERS section matched on net/rxrpc/ · linux-afs@lists.infradead.org · Supported
- Kernel module
- rxrpc
Check it on the machine
grep -w CONFIG_AF_RXRPC /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 rxrpcPrints 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 builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookworm, trixie, forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switch
- CONFIG_AF_RXRPC
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
- 7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsource recompute it - Attack vector
- network (AV:N)source
- EPSS
- 0.63%, higher than 49.1% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- net/rxrpc
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.6.143 | 6.6.145 | 8bbede0afced |
| 6.12.93 | 6.12.97 | 6563b4eb38c3 |
| 6.18.35 | 6.18.40 | d3b642cf95d4 |
| 7.1 | 7.1.5 | a962bc850859 |
| 7.1 | 7.2 | 16c8ae9735c5 |
| 7.0.11 | 0 | 0 |
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
- RxRPC runs over UDP/IP; a remote peer can deliver crafted DATA packets that are queued on the receive path and later processed in rxrpc_verify_data() via recvmsg/kernel_recv_data, with no local access required.
- AC:LAttack complexity, low
- An attacker can reliably trigger the bug by sending a zero-length RxRPC DATA packet (header-only skb so sp->len==0) to a listening service; no races or victim-specific state are needed beyond an active RxRPC/AFS endpoint.
- PR:NPrivileges required, none
- Incoming DATA packets are accepted and queued on new calls before Kerberos authentication completes, so an unauthenticated remote attacker can reach the vulnerable recvmsg path on internet-facing AFS/RxRPC servers without any local privileges.
- UI:NUser interaction, none
- On AFS/RxRPC servers the kernel automatically receives network DATA, queues it, and invokes rxrpc_kernel_recv_data through service callbacks; exploitation requires no victim user action such as mounting a filesystem or opening a file.
- S:UScope, unchanged
- The flaw causes a kernel NULL pointer dereference during in-kernel packet processing on the same host running the RxRPC/AFS service; it does not cross a VM, container, or IOMMU security boundary.
- C:NConfidentiality impact, none
- The failure mode is a NULL pointer dereference in skb_copy_bits()/subsequent recvmsg handling when rx_dec_buffer was never allocated; this is a pure crash path with no demonstrated or plausible arbitrary kernel memory read or information disclosure.
- I:NIntegrity impact, none
- No memory corruption, arbitrary write, or code-execution primitive is introduced; the bug dereferences a NULL decryption buffer during receive processing and results in kernel oops/panic rather than controlled data modification.
- A:HAvailability impact, high
- A successful trigger causes a kernel NULL pointer dereference during recvmsg data verification/decryption, which can oops or panic the host and deny service to all workloads on affected AFS/RxRPC servers until reboot.