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CVE-2026-23239
espintcp: Fix race condition in espintcp_close()
Published 2026-03-10 (7 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-2026-23239 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 | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | fixedDSA-6238-1 · 2026-04-30 · text | 6.12.85-1 | Update the kernel and reboot. DSA-6238-1 shipped the fix on 2026-04-30, in 6.12.85-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 6.19.6-1 | Update the kernel and reboot. Fixed in 6.19.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 6.19.6-1 | Update the kernel and reboot. Fixed in 6.19.6-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
This issue was discovered during a code audit. After cancel_work_sync() is called from espintcp_close(), espintcp_tx_work() can still be scheduled from paths such as the Delayed ACK handler or ksoftirqd. As a result, the espintcp_tx_work() worker may dereference a freed espintcp ctx or sk. The following is a simple race scenario: cpu0 cpu1 espintcp_close() cancel_work_sync(&ctx->work); espintcp_write_space() schedule_work(&ctx->work); To prevent this race condition, cancel_work_sync() is replaced with disable_work_sync().
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
- 2026-03-10 (7 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.10%, higher than 1.0% 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 | 6.12.75 | f7ad8b1d0e42 |
| 5.6 | 6.18.16 | 664e9df53226 |
| 5.6 | 6.19.6 | 022ff7f34758 |
| 5.6 | 7.0 | e1512c1db9e8 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DSA-6238-1 | 2026-04-30 | trixie 6.12.85-1 | 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:LAttack vector, local
- The attacker must be a local user to create a TCP socket and set the espintcp ULP via setsockopt(TCP_ULP). This cannot be triggered remotely without local socket access.
- AC:LAttack complexity, low
- The attacker controls both sides of the race: they trigger close() and control the remote peer (e.g., localhost connection) to send TCP ACKs that fire write_space, reliably creating the race condition.
- PR:LPrivileges required, low
- No capability checks exist in the TCP_ULP setsockopt path or espintcp_init_sk(). Any unprivileged local user can set up an espintcp ULP socket and trigger this bug.
- UI:NUser interaction, none
- No user interaction is required; the attacker autonomously creates the socket, sets the ULP, and triggers the race.
- S:UScope, unchanged
- The vulnerability is a kernel-level use-after-free that does not cross a security boundary such as a VM or sandbox.
- C:HConfidentiality impact, high
- The use-after-free on espintcp_ctx and sock structures allows an attacker to control freed object contents via heap spraying, enabling arbitrary kernel memory reads.
- I:HIntegrity impact, high
- The use-after-free enables heap spraying and arbitrary write primitives through the freed espintcp_ctx and sock structures, allowing potential kernel code execution.
- A:HAvailability impact, high
- The use-after-free causes kernel crashes (oops/panic) when the work function dereferences freed memory, providing reliable denial of service.