From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-80838: vxlan: keep the last remote linked during FDB flush
Date: Fri, 4 Sep 2026 17:53:05 +0200 [thread overview]
Message-ID: <2026090457-CVE-2026-80838-2cdb@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
vxlan: keep the last remote linked during FDB flush
A non-nexthop FDB entry is expected to have at least one remote while it
remains reachable through the FDB hash table. A filtered bulk flush
violates this invariant when every remote matches: It unlinks the last
remote in vxlan_fdb_dst_destroy() and only afterwards tells vxlan_flush()
to destroy the parent FDB entry.
An RCU reader can find the parent during this interval.
first_remote_rcu() then applies list_entry_rcu() to the empty list head,
producing an invalid remote pointer that the receive learning path can
read from and write to.
When a matching remote is the sole remaining remote, leave it linked and
ask the caller to destroy the entire FDB entry. vxlan_fdb_destroy() keeps
the remote attached while sending the deletion notification and removing
the parent from the lookup structures.
The Linux kernel CVE team has assigned CVE-2026-80838 to this issue.
Affected and fixed versions
===========================
Issue introduced in 6.7 with commit c499fccb71cb85902b5c5b9ce9c9ae6683e54a8f and fixed in 6.12.108 with commit 2a7c2f00843225d5f037676bca649321f3d024c7
Issue introduced in 6.7 with commit c499fccb71cb85902b5c5b9ce9c9ae6683e54a8f and fixed in 6.18.49 with commit a8820c8a7718327e96849782033e7c85a0f6bcfe
Issue introduced in 6.7 with commit c499fccb71cb85902b5c5b9ce9c9ae6683e54a8f and fixed in 7.1.13 with commit 8ba68fd6cdd1e3c92b92f25c7e48bf7bd51a183c
Issue introduced in 6.7 with commit c499fccb71cb85902b5c5b9ce9c9ae6683e54a8f and fixed in 7.2.3 with commit 4bbc76ee1b21d3bd045d6d819b2bacd30a6372ab
Issue introduced in 6.7 with commit c499fccb71cb85902b5c5b9ce9c9ae6683e54a8f and fixed in 7.3-rc1 with commit d5d4a7b538b52db63927773a8905fcd9f78a42e2
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-2026-80838
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:
drivers/net/vxlan/vxlan_core.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/2a7c2f00843225d5f037676bca649321f3d024c7
https://git.kernel.org/stable/c/a8820c8a7718327e96849782033e7c85a0f6bcfe
https://git.kernel.org/stable/c/8ba68fd6cdd1e3c92b92f25c7e48bf7bd51a183c
https://git.kernel.org/stable/c/4bbc76ee1b21d3bd045d6d819b2bacd30a6372ab
https://git.kernel.org/stable/c/d5d4a7b538b52db63927773a8905fcd9f78a42e2
reply other threads:[~2026-09-04 15:56 UTC|newest]
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