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 49C0D3D6486 for ; Fri, 11 Sep 2026 19:47:47 +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=1789156090; cv=none; b=SGSgsotFw6UOjIUYJVs9oFWlfMgO84IQBJ3R1AZ+CvWJTcEzYuYqf2mLcJeh46W545V0v22wSzf4K2/VrY1U2AEkyxcQrg9XQ12cJPoNvNWWc+OCLgT/L09emTwV7fpUe1RgiG8CWnVK5Gyb+oJTdHxbSJ9WqJezFAWzru6JLSU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789156090; c=relaxed/simple; bh=yv4rVdSGYbPmgMnK9cHiyO2RMXcMGO8U0jPXyOOybhY=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=dbkcLCGa3DxrY9FQKqE+sty15uaGC9dxlTMhV8tuO4dURvxk6JivQqBqTJgqzFyvGJl+6VHZI5NusfM7ulCcVzBgvA7TsSRrJ0C/dseOtA3Dy8CaTCqbplZxR01axLkYWgsY9mldmnBwlsUkHU4TtXSRTURyZtn3mbwzNENt7W0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=K/R/aHEK; 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="K/R/aHEK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7CEB51F00899; Fri, 11 Sep 2026 19:47:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789156067; bh=2nPNqSmn0btRH0xF5B9esuHP8eGOJ3TPwdpUhS0BkCU=; h=From:To:Cc:Subject:Date:Reply-To; b=K/R/aHEKFqaW5xnOeH2rWCc3SE3is3pCiWzKrjvimyKVf/6G0ttMqj20lw0NErKW0 mAaf2kDALmqEYu2CsP+oMbLyklzGhUf7CJXH1tw9j2rU363OTF4IHtmxnRnYB2oX5u dY9UGoSOrHmC9x3XNoocWsP8nK8wgS/Yvvq3vF4I= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-80976: seg6: reset IP6CB after IPv6 decapsulation Date: Fri, 11 Sep 2026 21:41:22 +0200 Message-ID: <2026091145-CVE-2026-80976-ff9d@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=3627; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=M7W/rdFzzY8sQ8Vd9AQsosxHUPMTjVpqtLBsW9EDs/o=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlLIm2tHDzPrEiZUe/qItDH2f73tUDi/ScnGXLXVCxp3 X4mVOxaRywLgyATg6yYIsuXbTxH91ccUvQytD0NM4eVCWQIAxenAEwkYBLD/PhS///79Dmbnx+f 5q/ZHnAp7oXeDoYF6yaGzBHuKL2z7kvnvT8yyXLbuR5wAQA= 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: seg6: reset IP6CB after IPv6 decapsulation decap_and_validate() pulls the outer SRv6 headers and makes the inner packet the skb network header. The IPv6 control block still contains values collected while parsing the outer packet, including nhoff and extension-header flags. End.DX6 and End.DT6 route the inner IPv6 packet directly to the IPv6 input path. An unprivileged user can reach End.DT6 from a user and net namespace by installing a local SID and injecting an outer packet with Hop-by-Hop and Destination Options headers followed by an SRH and a minimal inner IPv6 packet. The outer extension headers leave a large nhoff in IP6CB. After decapsulation, ip6_protocol_deliver_rcu() uses that stale offset on the inner packet and reads beyond the skb head. KASAN reports: BUG: KASAN: slab-out-of-bounds in ip6_protocol_deliver_rcu ip6_protocol_deliver_rcu+0x1118/0x1450 ip6_input_finish+0x11b/0x240 seg6_local_input_core+0xed/0x2e0 lwtunnel_input+0x1e9/0x4e0 ipv6_rthdr_rcv+0x525f/0x6c50 ip6_protocol_deliver_rcu+0xcb7/0x1450 Before clearing IP6CB for an inner IPv6 packet, save its incoming interface index and L3 slave state. Restore both after the clear and set nhoff to the inner IPv6 base-header nexthdr field. Use IP6CB(skb)->iif rather than skb->skb_iif because VRF processing can replace skb_iif with the L3 master while IP6CB keeps the receiving interface. Preserve IP6SKB_L3SLAVE for the same reason. The Linux kernel CVE team has assigned CVE-2026-80976 to this issue. Affected and fixed versions =========================== Issue introduced in 4.14 with commit d7a669dd2f8ba07a17423f4ad586dfc0379882f7 and fixed in 6.12.109 with commit 2b154e96fcb3f01fd42765c64e0a56820fbc16eb Issue introduced in 4.14 with commit d7a669dd2f8ba07a17423f4ad586dfc0379882f7 and fixed in 6.18.50 with commit cfa186a0857a0f831dfca67b16bbc40ecfdf3280 Issue introduced in 4.14 with commit d7a669dd2f8ba07a17423f4ad586dfc0379882f7 and fixed in 7.2.4 with commit c73fb911e02b9a766c950bc9707f3e3a96ffd702 Issue introduced in 4.14 with commit d7a669dd2f8ba07a17423f4ad586dfc0379882f7 and fixed in 7.3-rc1 with commit f967455fb2a5a2079b9eb5823e9ccf359174bf9f 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-2026-80976 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/ipv6/seg6_local.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/2b154e96fcb3f01fd42765c64e0a56820fbc16eb https://git.kernel.org/stable/c/cfa186a0857a0f831dfca67b16bbc40ecfdf3280 https://git.kernel.org/stable/c/c73fb911e02b9a766c950bc9707f3e3a96ffd702 https://git.kernel.org/stable/c/f967455fb2a5a2079b9eb5823e9ccf359174bf9f