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CVE-2026-53151
rxrpc: Fix the ACK parser to extract the SACK table for parsing
Published 2026-06-25 (4 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-2026-53151 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-6381-1 · 2026-07-05 · text | 6.12.95-1 | Update the kernel and reboot. DSA-6381-1 shipped the fix on 2026-07-05, in 6.12.95-1. 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
Fix modification of the received skbuff in rxrpc_input_soft_acks() and a potential incorrect access of the buffer in a fragmented UDP packet (the packet would probably have to be deliberately pre-generated as fragmented) when AF_RXRPC tries to extract the contents of the SACK table by copying out the contents of the SACK table into a buffer before attempting to parse AF_RXRPC assumes that it can just call skb_condense() and then validly access the SACK table from skb->data and that it will be a flat buffer - but skb_condense() can silently fail to do anything under some circumstances. Note that whilst rxrpc_input_soft_acks() should be able to parse extended ACKs, the rest of AF_RXRPC doesn't currently support that. Further, there's then no need to call skb_condense() in rxrpc_input_ack(), so don't.
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/input.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
- 2026-06-25 (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
- 0.67%, higher than 51.1% 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 |
|---|---|---|
| 6.2 | 6.6.144 | 5d1ae4e17a3e |
| 6.2 | 6.12.95 | 775c5e89272a |
| 6.2 | 6.18.36 | 566c4c1244de |
| 6.2 | 7.0.13 | 224298450be5 |
| 6.2 | 7.1 | 333b6d5bb9f8 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DSA-6381-1 | 2026-07-05 | trixie 6.12.95-1 | 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
- AF_RXRPC processes ACK packets received over UDP from a network peer. A malicious remote peer can send a crafted fragmented RxRPC ACK for an active transmitting call.
- AC:LAttack complexity, low
- The needed fragmented/non-linear skb and ACK fields are attacker-controlled packet properties, and valid call state can be created by participating as the RxRPC peer. No race or condition outside the attacker's control is required.
- PR:NPrivileges required, none
- The vulnerable parser is reached from network packet receive after protocol matching checks, not after any local privilege check. A remote RxRPC peer does not need an account or kernel privilege on the target.
- UI:NUser interaction, none
- Once an RxRPC service/client call exists, the malicious ACK is processed automatically by the kernel receive path. No victim user action is needed to parse the packet.
- S:UScope, unchanged
- The corruption occurs inside the target kernel's networking/RxRPC memory management context. It does not inherently cross into another security authority such as a hypervisor boundary.
- C:HConfidentiality impact, high
- The bug performs out-of-bounds reads past the skb linear area into kernel memory while parsing attacker-supplied ACK state. As kernel memory corruption with read exposure potential, confidentiality impact is high.
- I:HIntegrity impact, high
- The soft-ACK loop performs read-modify-write shifts through the out-of-bounds pointer, corrupting skb tailroom, skb_shared_info, or adjacent slab memory. This is an out-of-bounds write primitive in kernel memory.
- A:HAvailability impact, high
- Corrupting skb metadata or adjacent kernel objects can readily trigger an oops, panic, or memory-management failure. The crafted ACK can be sent repeatedly to sustain denial of service.