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CVE-2026-72041
espintcp: use sk_msg_free_partial to fix partial send
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem net/xfrm. 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-2026-72041 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 | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| 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
sk_msg_free_partial() ensures consistency of the skmsg at every iteration, without having to manually handle uncharges and offsets. This simplifies the code, and fixes some bugs in skmsg accounting when we don't send the full contents.
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/xfrm/espintcp.c
- What this is
- NETWORKING [IPSEC]MAINTAINERS section matched on net/xfrm/ · netdev@vger.kernel.org · Maintained
- Kernel module
- none to look for. The file would have gone into espintcp, and Debian does not compile it into that module, so finding espintcp in lsmod would say nothing about this CVE.
Check it on the machine
grep -wE 'CONFIG_XFRM|CONFIG_XFRM_ESPINTCP' /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_XFRM, CONFIG_XFRM_ESPINTCP
- 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
- 0.76%, higher than 54.2% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/xfrm
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.6 | 5.10.266 | 518dcb84b997 |
| 5.6 | 5.15.217 | 4ea8c051b4bd |
| 5.6 | 6.1.184 | a977f78adce4 |
| 5.6 | 6.6.145 | 54d73f18f891 |
| 5.6 | 6.12.97 | 14c0b42c8a2c |
| 5.6 | 6.18.40 | a66d45e0ce6d |
| 5.6 | 7.1.5 | a338ce41bc93 |
| 5.6 | 7.2 | 007800408002 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | 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
- espintcp carries IKE/IPsec over TCP (RFC 8229) on internet-facing VPN gateways; a remote TCP peer can induce partial sends during server outbound IKE responses by shrinking/draining the receive window, corrupting skmsg state without local access.
- AC:LAttack complexity, low
- The attacker controls both sides of the TCP connection and can reliably force partial sends by not reading, advertising a zero window, or resetting mid-transfer; no race or memory-layout conditions outside attacker control are required.
- PR:NPrivileges required, none
- Exploitation needs no credentials on the target—an unauthenticated remote peer during pre-auth IKE-over-TCP can trigger server sends; locally any user can set TCP_ULP to espintcp and sendmsg without CAP_NET_ADMIN or XFRM configuration.
- UI:NUser interaction, none
- No victim user action is required; once an espintcp TCP endpoint exists, the remote peer alone drives the partial-send condition through normal TCP flow control during server transmission.
- S:UScope, unchanged
- Impact is kernel heap corruption and privilege escalation within the host kernel; it does not cross VM, IOMMU, or sandbox security boundaries.
- C:HConfidentiality impact, high
- Incorrect skmsg/page accounting on partial sends causes use-after-free and double-free of scatterlist pages; freed objects can be reallocated and read for arbitrary kernel memory disclosure.
- I:HIntegrity impact, high
- Corrupted scatterlist offsets and page refcount errors yield exploitable kernel memory corruption primitives that can enable arbitrary writes and local privilege escalation.
- A:HAvailability impact, high
- Double-free and invalid page references in the send/resume path can oops or panic the kernel; a remote or local attacker can repeat the trigger via sustained partial-send pressure.