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CVE-2026-52935
xfrm: espintcp: do not reuse an in-progress partial send
Published 2026-06-24 (4 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-2026-52935 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-4665-1 · 2026-07-03 · text | 6.1.176-1 | Update the kernel and reboot. DLA-4665-1 shipped the fix on 2026-07-03, in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. 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
espintcp keeps a single in-flight transmit in ctx->partial. Before building a new sk_msg, espintcp_sendmsg() first tries to flush that state through espintcp_push_msgs(). For blocking callers, espintcp_push_msgs() may return success even when the previous partial send is still pending. espintcp_sendmsg() would then reinitialize emsg->skmsg and reuse ctx->partial while the old transfer still owns that state. Do not rebuild the send message when ctx->partial is still in progress. If espintcp_push_msgs() returns with emsg->len still set, fail the new send instead of overwriting the live partial state. This is a memory-safety fix: reusing the live partial-send state can leave a stale offset attached to a new sk_msg and lead to an out-of- bounds read in the send path. tcp_sendmsg_locked() already handles waiting for send buffer memory, so the fix here is just to preserve espintcp's one-message-at-a-time transmit state.
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
- 2026-06-24 (4 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
- 0.12%, higher than 1.7% 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 | 5.10.259 | 6564e9c7af7e |
| 5.6 | 5.15.210 | 1777ceac4bea |
| 5.6 | 6.1.176 | 8c6c691bf062 |
| 5.6 | 6.6.143 | aa82a078f70f |
| 5.6 | 6.12.94 | ba21439302db |
| 5.6 | 6.18.36 | f9b38a8fbfa0 |
| 5.6 | 7.0.13 | 37487d55bf33 |
| 5.6 | 7.1 | c381039ade2e |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4671-1 | 2026-07-05 | bullseye 6.1.176-1~deb11u1 | tracker |
| DLA-4665-1 | 2026-07-03 | bookworm 6.1.176-1 | tracker |
| DLA-4664-1 | 2026-07-03 | bullseye 5.10.259-1 | 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 vulnerable code is reached through local socket syscalls: an attacker creates/uses a TCP socket, sets `TCP_ULP` to `espintcp`, and calls send/sendmsg. It is not directly triggerable by unauthenticated network packets alone.
- AC:LAttack complexity, low
- The attacker can create the needed partial-send condition by controlling the TCP peer or receiver behavior and filling the send buffer, then issuing another send. No race or condition outside attacker control is required.
- PR:LPrivileges required, low
- Setting an already-registered TCP ULP does not require CAP_NET_ADMIN, and ordinary local users can create TCP sockets and call setsockopt/sendmsg. XFRM administration is privileged, but it is not required for this lowest-privilege path to `espintcp_sendmsg`.
- UI:NUser interaction, none
- Exploitation does not require any victim user action after the attacker has local code execution. The attacker directly drives the socket operations.
- S:UScope, unchanged
- The impact remains within the kernel and its managed resources on the same host. This is not a VM escape, IOMMU bypass, or cross-authority boundary violation.
- C:HConfidentiality impact, high
- The stale partial-send offset can produce an out-of-bounds read in the TCP send path, potentially exposing kernel memory through transmitted data. Because the read is not strictly bounded to a small fixed disclosure, high confidentiality impact is appropriate.
- I:HIntegrity impact, high
- The corrupted espintcp/sk_msg state can build invalid bvec/socket-buffer references and disturb page or send-buffer accounting, which is a plausible kernel memory integrity primitive. Under the required higher-severity rule for uncertainty, this is scored as high integrity impact.
- A:HAvailability impact, high
- The invalid scatterlist/bvec state can lead to kernel warnings, invalid page references, refcount/accounting corruption, or crashes in the send/cleanup path. A local attacker can repeat the trigger, so availability impact is high.