CVE-2026-52935: xfrm: espintcp: do not reuse an in-progress partial send

CVE-2026-52935: xfrm: espintcp: do not reuse an in-progress partial send

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

xfrm: espintcp: do not reuse an in-progress partial send

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.

The Linux kernel CVE team has assigned CVE-2026-52935 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.6 with commit e27cca96cd68fa2c6814c90f9a1cfd36bb68c593 and fixed in 5.10.259 with commit 6564e9c7af7e1dc7bfe7f3093b728abe484d7630
	Issue introduced in 5.6 with commit e27cca96cd68fa2c6814c90f9a1cfd36bb68c593 and fixed in 5.15.210 with commit 1777ceac4bea5e568a5ad44b7f9bb219c1db21b6
	Issue introduced in 5.6 with commit e27cca96cd68fa2c6814c90f9a1cfd36bb68c593 and fixed in 6.1.176 with commit 8c6c691bf062dc0753a139a4ab8cb92a70fcf8f3
	Issue introduced in 5.6 with commit e27cca96cd68fa2c6814c90f9a1cfd36bb68c593 and fixed in 6.6.143 with commit aa82a078f70f7ff88ba7d1017134e79d1ac140f2
	Issue introduced in 5.6 with commit e27cca96cd68fa2c6814c90f9a1cfd36bb68c593 and fixed in 6.12.94 with commit ba21439302db9a82fe4edbed1e38a97271529421
	Issue introduced in 5.6 with commit e27cca96cd68fa2c6814c90f9a1cfd36bb68c593 and fixed in 6.18.36 with commit f9b38a8fbfa07f1deaf7ee1eb38fa8b21ea13990
	Issue introduced in 5.6 with commit e27cca96cd68fa2c6814c90f9a1cfd36bb68c593 and fixed in 7.0.13 with commit 37487d55bf3300e3d2c1368da5c2bd3e3834ea4f
	Issue introduced in 5.6 with commit e27cca96cd68fa2c6814c90f9a1cfd36bb68c593 and fixed in 7.1 with commit c381039ade2e161ab08c0eda73c4f8b9a7115928

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-52935
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/xfrm/espintcp.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/6564e9c7af7e1dc7bfe7f3093b728abe484d7630
	https://git.kernel.org/stable/c/1777ceac4bea5e568a5ad44b7f9bb219c1db21b6
	https://git.kernel.org/stable/c/8c6c691bf062dc0753a139a4ab8cb92a70fcf8f3
	https://git.kernel.org/stable/c/aa82a078f70f7ff88ba7d1017134e79d1ac140f2
	https://git.kernel.org/stable/c/ba21439302db9a82fe4edbed1e38a97271529421
	https://git.kernel.org/stable/c/f9b38a8fbfa07f1deaf7ee1eb38fa8b21ea13990
	https://git.kernel.org/stable/c/37487d55bf3300e3d2c1368da5c2bd3e3834ea4f
	https://git.kernel.org/stable/c/c381039ade2e161ab08c0eda73c4f8b9a7115928