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 E072E58E2AE for ; Fri, 11 Sep 2026 19:57:37 +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=1789156662; cv=none; b=FUy7sa8Ndv0X5qfIJbVaXSUE1O9NvJ9/LNBUBfnWgZOlcdf8OmX6kDK4t3b2BX3cVo3DB/g0TBUhIP5Vq3hsMuJq/Ih5m1KltKemaBGym0JP7jnv1SYmakWUK2CVQ18m98lwbSyGB0a0MaA/sNgXCHXfxToic84J/vgwjEviA0Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789156662; c=relaxed/simple; bh=jybFaCyUEP6hEQR81wabCA4AZ4DouaU+J7hMJsESm7Q=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=jAgwdBRc2IO8THoibNlm2j55QvZNhy7MDtVhFx5gCO39tvw5nuxFO/EllvpJ+b5Sz6yGVBAidMtJfKvVDlEWpXGDz7nnK1PWITAV3flFVQSfkcbkFZIv8dQleu+ZWAhOVraaYyeEWyEwscxqggR27xzZdRKkEX4Fby+h9waoORU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=WLrq2dyD; 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="WLrq2dyD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3FC841F00899; Fri, 11 Sep 2026 19:57:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789156654; bh=5XBbTIu7bOmHR85NyERYtmReG5VNyvCz+EHDcc6Zkrc=; h=From:To:Cc:Subject:Date:Reply-To; b=WLrq2dyDvY2/TVZYZF5LiLshT81jSxOr9WmA7BbtdmMST3UBe13/Yv0LVHCcd93k5 vjiKnhAqxVaUe1tGOcCcPyaILkZBOetEXPzQw/+qOOPlLlJ25+srGtCNvWPYhSq33V HS71Y7AzrVCvAWWQuxvKldxWhMONil4fOsIOwm+M= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-89555: mpls: reload header after pskb_may_pull() Date: Fri, 11 Sep 2026 21:44:04 +0200 Message-ID: <2026091122-CVE-2026-89555-5464@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=3686; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=aOz87hT3NLWb6eQB+pdH7W+Q3sIKC+qHPwAeP7h0qQg=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlLIpMe3159Yf6nJvUTbjn/7QRnBNkfPaC9PVJsz9GoH r8dPU0TO2JZGASZGGTFFFm+bOM5ur/ikKKXoe1pmDmsTCBDGLg4BWAih28yzGZdd8ng1CPZMwEn C19XMM34HOp7diXDPMu/bnb5eznrj3EbGHKEsd5W9O/QBQA= 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: mpls: reload header after pskb_may_pull() mpls_select_multipath() calls mpls_multipath_hash() to choose a nexthop when an MPLS route has multiple nexthops. While walking the MPLS label stack, the hash routine caches hdr for the current label. After finding the bottom-of-stack label, it calls pskb_may_pull() before reading the inner IP header. If an skb is constructed with the inner IP header in nonlinear data and insufficient tailroom in the linear head, pskb_may_pull() calls pskb_expand_head() to replace the skb head and free the old one. This leaves hdr pointing to freed memory. The IPv6 path can invalidate hdr again when it performs a second pull for the larger header. The issue was found through static analysis. A reproducer sending a legal Geneve packet through a bareudp/MPLS multipath setup triggered the same KASAN report in 2 of 2 unpatched runs: BUG: KASAN: slab-use-after-free in mpls_select_multipath Read of size 1 at addr ffff88800ecc6e20 by task ksoftirqd/1/23 Call Trace: mpls_select_multipath mpls_forward __netif_receive_skb_list_core netif_receive_skb_list_internal napi_complete_done gro_cell_poll __napi_poll net_rx_action Freed by task 23: kfree pskb_expand_head __pskb_pull_tail mpls_select_multipath Reload hdr from the current skb head after each successful pull before deriving the inner IPv4 or IPv6 header pointer. The Linux kernel CVE team has assigned CVE-2026-89555 to this issue. Affected and fixed versions =========================== Issue introduced in 4.10 with commit 9f427a0e474a67b454420c131709600d44850486 and fixed in 6.12.109 with commit fed638a248116b8a249bd4202d28e5934bdc65ad Issue introduced in 4.10 with commit 9f427a0e474a67b454420c131709600d44850486 and fixed in 6.18.50 with commit d82b90a38c2ca8a0694428eab0e9551c23f2447d Issue introduced in 4.10 with commit 9f427a0e474a67b454420c131709600d44850486 and fixed in 7.2.4 with commit 49d38c1b4390412f8950d33dfaee0ccbd17beb81 Issue introduced in 4.10 with commit 9f427a0e474a67b454420c131709600d44850486 and fixed in 7.3-rc1 with commit 29e63b8d9fc150cc191b1c6eb7e16e1247e1b650 Issue introduced in 4.9.8 with commit ad864d9fce0ec56cc8f6afe5c6a0e6d7f484b9eb 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-2026-89555 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/mpls/af_mpls.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/fed638a248116b8a249bd4202d28e5934bdc65ad https://git.kernel.org/stable/c/d82b90a38c2ca8a0694428eab0e9551c23f2447d https://git.kernel.org/stable/c/49d38c1b4390412f8950d33dfaee0ccbd17beb81 https://git.kernel.org/stable/c/29e63b8d9fc150cc191b1c6eb7e16e1247e1b650