From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 51BCC577E3C for ; Fri, 11 Sep 2026 19:50:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789156230; cv=none; b=GwfsbijmMvodxw5xAs9J1gdyA9ADQ/AdNKUpXBtUNgLvsAtzeepGKAZfvd1Gp0vdwEr4aCEMUI5TYqjTbXwVbIiZ3u/wI0X01o/F26MEP249jLjuJ5WnGrbeM6w8a/2mAEhG4EBZkFBw7CDBAKu1zkJpaHJCWk7+VtPdF6l3YVg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789156230; c=relaxed/simple; bh=JheH3aJFEa7icuqVxl4VkHmn+azG1+6ZLyvN9MjsyBU=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=U8lkTYAb6TojD4RfW/BYcgNuTcBhx9CAlD0zwrinrDGhfs55PzCzliiOlQ4zq0MgIqkXqKKn2vGRQ6P/bhSudjwonidn0XUakHCwM4EyZtD7m23091rVTXShnYX0uf7BTy4YlwM5SjMd6K4GxdhSe0ygwt/KBXfgkqu09R8Kna4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=dnfhYVCz; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="dnfhYVCz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 11DFF1F000FF; Fri, 11 Sep 2026 19:50:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789156224; bh=X0mydMea1ZHAfvmyyTBymRZWyYn7IyKB/xZwXZaoLJs=; h=From:To:Cc:Subject:Date:Reply-To; b=dnfhYVCz/hyq+KlwW/46+G4GZr+0+/1roFJ5KO3J+RUWeOW3cT2JYq8civ7ek59gM EsYVIk2uifk+N2rAR9QTe4xM4b0/6hkpo3zphmL8zoEI2F0mxeBueB8t8/fGNh1Jbr K+A27HQp/EnTvtskC8PTRhDQJrRd3dIWAqBZoN0E= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-80995: net: mctp: hold a reference to the route device in mctp_route_lookup() Date: Fri, 11 Sep 2026 21:41:41 +0200 Message-ID: <2026091149-CVE-2026-80995-5154@gregkh> X-Mailer: git-send-email 2.55.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2957; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=N0QvaC30ci64tduhyRWCGBXveTIzjEjlpiJ9v/Jqs5s=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlLIh3nenyeldMq4h9iUf3/3IJ7S2K/rG9o487evsnzy yZG58q0jlgWBkEmBlkxRZYv23iO7q84pOhlaHsaZg4rE8gQBi5OAZjI2wkM873z9fj1Xvmrh/H9 E+P4/0RdZgrjVIb5fstmsuryfp/PzBNTuK1ti6yVzOTLAA== X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: net: mctp: hold a reference to the route device in mctp_route_lookup() mctp_route_lookup() uses rt->dev without holding a reference on it. mctp_route_lookup_single() returns the route under RCU only, so the route's device can be torn down concurrently: mctp_dev_put() drops the last reference and synchronously kfree()s mdev->addrs. mctp_dev_saddr() then reads rt->dev->addrs[0], giving a use-after-free reachable by an unprivileged local AF_MCTP user on the receive/forwarding path (no CAP_NET_RAW required): BUG: KASAN: slab-use-after-free in mctp_route_lookup Read of size 1 at addr ... by task mctp_uaf/... mctp_route_lookup mctp_pkttype_receive Freed by task ...: kfree mctp_dev_put mctp_dev_notify In the same window mctp_dst_from_route() -> mctp_dev_hold() also increments a refcount that has already reached zero ("refcount_t: addition on 0 ... mctp_dev_hold"). This reintroduces the use-after-free class of CVE-2023-3439: the source address lookup was moved ahead of the point where the destination takes its device reference. Take a reference with refcount_inc_not_zero() before touching rt->dev, skip a device that is already dead, and drop the reference once the destination has taken its own. The Linux kernel CVE team has assigned CVE-2026-80995 to this issue. Affected and fixed versions =========================== Issue introduced in 7.1 with commit 22cb45afd221b9e4f2a1dcc74a8ff645b7293aa1 and fixed in 7.2.4 with commit cc561f8af25586300c2f9d285babb163b866b293 Issue introduced in 7.1 with commit 22cb45afd221b9e4f2a1dcc74a8ff645b7293aa1 and fixed in 7.3-rc1 with commit 408da1df18116c971c3392e21e50586688cd3fbf 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-2026-80995 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/mctp/route.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/cc561f8af25586300c2f9d285babb163b866b293 https://git.kernel.org/stable/c/408da1df18116c971c3392e21e50586688cd3fbf