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 7EB543A3830 for ; Sun, 19 Jul 2026 15:03:35 +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=1784473416; cv=none; b=GKRNO36A7LVnK2lI+cy5+iJ4JI+/uRhhq81iRKXUnqGbDw2nSmiiYDO1UUWr5WmkJzoK8WHUwMxHPuLTMGuv9lJVoZdO4d/sbYTlXrokA50ENfOPoYG2/e1IEm/mGTuDYwTbEynzqQDCWGB2c4bxHwhgtme/TGaq36asgAwhlII= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784473416; c=relaxed/simple; bh=tUAwfANkKwi6pp0THNm40tg17Es1i/2/bymwoKyk5NY=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=hZp4dbAriAse8eSJ1j3wOk7F6uJxJSD42tY3ukXwLPTu6o4B3geP3i1ympKhipMRlx3bItcbcnh94EaiL2YzJBC2cXE0/oRJQRwOaj0DoHSEMHZYHyzNEjUWIGmmwCIc4hUY474S4X5dZHGPKqZ4lmCmFQ3hICad8l+7ATRB9FU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=J06SjjFZ; 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="J06SjjFZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A91861F000E9; Sun, 19 Jul 2026 15:03:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784473415; bh=Ay1Dbbx6cfXKXQawQV1z6zh6DG2yOmzMQxJSYhS4qZA=; h=From:To:Cc:Subject:Date:Reply-To; b=J06SjjFZmo3a2fR2QRpmh8rG9Y1Maw6dv097ZNkLCqWU6L9UOVym/VUmA9yC90hrn 00G7pGE4tXWBlecVvUkcYS+5ogv6Oh6X29rLFEAQ9w3munngP0aCt6fjvKMiCPRM/2 FP7OTeCOcwOHZCgrOc3QthwuhKYBDFFa0yt7/uh4= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-64009: xfrm: Check for underflow in xfrm_state_mtu Date: Sun, 19 Jul 2026 16:57:49 +0200 Message-ID: <2026071908-CVE-2026-64009-4587@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=4305; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=3J81kcsms7YgLFz+tUdoM5fFz1k2JCrH0qFj2HQP0qg=; b=owGbwMvMwCRo6H6F97bub03G02pJDFkxTztarqjax5qHbDy3yMSo4O7/B3HeTt5zvwkVHfWbP Ku09a9zRywLgyATg6yYIsuXbTxH91ccUvQytD0NM4eVCWQIAxenAEzkGTfDLOYZEypr62OaDxyp ELZTVnr4d5+uKsMc3psOkgoL97v3fVli/8Y3KDjNt9gSAA== 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: xfrm: Check for underflow in xfrm_state_mtu Leo Lin reported OOB write issue in esp component: xfrm_state_mtu() returns u32 but performs its arithmetic in unsigned modulo-2^32 space using an attacker-influenced "header_len + authsize + net_adj" subtracted from a small "mtu" argument. A nobody user can install an IPv4 ESP tunnel SA with a large authentication key (XFRMA_ALG_AUTH_TRUNC, e.g. hmac(sha512), 64-byte key, 64-byte trunc), configure a small interface MTU (68 bytes), and set XFRMA_TFCPAD to a large value. When a single UDP datagram is then sent through the tunnel, xfrm_state_mtu() underflows to a near-2^32 value, and esp_output() consumes it as a signed int via: padto = min(x->tfcpad, xfrm_state_mtu(x, mtu_cached)) esp.tfclen = padto - skb->len (assigned to int) esp.tfclen ends up negative (e.g. -207). It is sign-extended to size_t when passed to memset() inside esp_output_fill_trailer(), producing a ~16 EB write of zeroes at skb_tail_pointer(skb). KASAN logs it as "Write of size 18446744073709551537 at addr ffff888...". Check for underflow and return 1. This causes the sendmsg attempt to fail with ENETUNREACH. The Linux kernel CVE team has assigned CVE-2026-64009 to this issue. Affected and fixed versions =========================== Issue introduced in 2.6.22 with commit c5c2523893747f88a83376abad310c8ad13f7197 and fixed in 5.10.259 with commit 8014f70c4e6e5ab101ae3860a614e65e988372e3 Issue introduced in 2.6.22 with commit c5c2523893747f88a83376abad310c8ad13f7197 and fixed in 5.15.210 with commit 1021d2877b689a648b27815c854557a917122e93 Issue introduced in 2.6.22 with commit c5c2523893747f88a83376abad310c8ad13f7197 and fixed in 6.1.176 with commit 2a41b1b31c61c52b972278ce1732a1443f5e89ed Issue introduced in 2.6.22 with commit c5c2523893747f88a83376abad310c8ad13f7197 and fixed in 6.6.143 with commit fccd685b32df5aaf6bad4381eeda216468e283f0 Issue introduced in 2.6.22 with commit c5c2523893747f88a83376abad310c8ad13f7197 and fixed in 6.12.93 with commit 820e501be8aee4b365d218d83227b314309c5fda Issue introduced in 2.6.22 with commit c5c2523893747f88a83376abad310c8ad13f7197 and fixed in 6.18.35 with commit 82ac903e0b519849647657b8c48d21237ada06a2 Issue introduced in 2.6.22 with commit c5c2523893747f88a83376abad310c8ad13f7197 and fixed in 7.0.12 with commit 3db50ceeacb52806d8fe86fb1dfe944df0b9f789 Issue introduced in 2.6.22 with commit c5c2523893747f88a83376abad310c8ad13f7197 and fixed in 7.1 with commit 742b04d0550b0ec89dcbc99537ec88653bd1ad90 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-2026-64009 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/xfrm_state.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/8014f70c4e6e5ab101ae3860a614e65e988372e3 https://git.kernel.org/stable/c/1021d2877b689a648b27815c854557a917122e93 https://git.kernel.org/stable/c/2a41b1b31c61c52b972278ce1732a1443f5e89ed https://git.kernel.org/stable/c/fccd685b32df5aaf6bad4381eeda216468e283f0 https://git.kernel.org/stable/c/820e501be8aee4b365d218d83227b314309c5fda https://git.kernel.org/stable/c/82ac903e0b519849647657b8c48d21237ada06a2 https://git.kernel.org/stable/c/3db50ceeacb52806d8fe86fb1dfe944df0b9f789 https://git.kernel.org/stable/c/742b04d0550b0ec89dcbc99537ec88653bd1ad90