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 7120C4A8432 for ; Fri, 11 Sep 2026 19:47:54 +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=1789156087; cv=none; b=PFGS1+V3VzTEODuu4LSnUVgjnbMEqw5J5e6skwl02STWpMtuRXKTeWfEWDvDzQh4Cvz4XlD0GhjiGZoq9OJ8b9IcIPbbWZ7KJ5VaTnWWQb0JZBTpvBVDilSYKYESlATead6fpxFNyxDNPDXmAjUCvBr9GcZsWHQEeJvLEJsYPEw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789156087; c=relaxed/simple; bh=QpoYkEhsVnauA5HzX62pFaGT+C1c4AvxG7M147vN6nI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=YoqVIpoLUaWFkUvKtBnKN3fmkiBwadT3oQg/3+K1n+Gae5P3nTykkQUfo8RyGdeHDDr03AbDdzXSS9p62Y9MRdeeDGEo6z3fKSC1obaGaRDFX7q4QiZh9c4XfpG+LXR/8iB0tUdAUdhQEY1W6myGD+XOiuwq0ZLy9ewmlYCZVdQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=TF98tZEK; 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="TF98tZEK" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 888E31F00893; Fri, 11 Sep 2026 19:47:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789156073; bh=reBNXDm2dxzglwHIwuRXl3zSZ+w7kNxuiuswdwEo2Tw=; h=From:To:Cc:Subject:Date:Reply-To; b=TF98tZEKVEZLR9BaORHPjEMah2PySayxgGiKwBTACwq0isBEFgsqcZYqFfTKeRgy3 VIPDcYUAxFt1iwopwN94IpsX44VM58N1rIr8yBs19BHrqeyC+3qxKATvGt/gDdyY7g jl7dXFwOjXGxFKqFWePI7jhz7kQ6aLu8voCQV+Ac= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-80978: net: cap advertised IP tunnel headroom Date: Fri, 11 Sep 2026 21:41:24 +0200 Message-ID: <2026091146-CVE-2026-80978-10ac@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=3014; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=5blYtEJ6m+0k/3Jb66Sj9fFgZXA24fPAEKauGX076t8=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlLIu08GPZ+lOH/L3mDe22lOW9BCYOb4b9nBrzT20NKT nIdC2bqiGVhEGRikBVTZPmyjefo/opDil6Gtqdh5rAygQxh4OIUgInMvsow3+WAxxwdkx+5uV0B /361qqfO2Nd3gmHB6qbHfQYXvcWdiqaErlNyvPBK21UcAA== 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: cap advertised IP tunnel headroom IP tunnel devices derive their advertised needed_headroom from lower output devices. A stack of user-created devices can make the derived value larger than the 16-bit skb header offsets can represent. Once IP output reserves it, skb head expansion can wrap those offsets. The runtime transmit path already caps a growing needed_headroom at 512. Apply the same cap when tunnel configuration publishes needed_headroom derived from a lower output device. Capping the advertised value is safe: IP tunnel transmit still expands the skb when a packet needs more headroom. A nonsensical stacked configuration can therefore incur an extra reallocation, but it cannot publish an unbounded reservation to upper layers. The Linux kernel CVE team has assigned CVE-2026-80978 to this issue. Affected and fixed versions =========================== Issue introduced in 3.11 with commit 1a37e412a0225fcba5587f24c0dfc7636efc8b69 and fixed in 6.12.109 with commit bc4e05ae66c9797a0972ac44326e69c5305e0020 Issue introduced in 3.11 with commit 1a37e412a0225fcba5587f24c0dfc7636efc8b69 and fixed in 6.18.50 with commit af0ee8f04bea22cdb331fa3509e17f81b48938ad Issue introduced in 3.11 with commit 1a37e412a0225fcba5587f24c0dfc7636efc8b69 and fixed in 7.2.4 with commit 9144f2c53a04465a6878172b523f640313c5559e Issue introduced in 3.11 with commit 1a37e412a0225fcba5587f24c0dfc7636efc8b69 and fixed in 7.3-rc1 with commit 6b222adeb9340306e2ff97127c76117abb9b3df8 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-2026-80978 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: include/net/ip_tunnels.h net/ipv4/ip_tunnel.c net/ipv6/ip6_gre.c net/ipv6/ip6_tunnel.c net/ipv6/sit.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/bc4e05ae66c9797a0972ac44326e69c5305e0020 https://git.kernel.org/stable/c/af0ee8f04bea22cdb331fa3509e17f81b48938ad https://git.kernel.org/stable/c/9144f2c53a04465a6878172b523f640313c5559e https://git.kernel.org/stable/c/6b222adeb9340306e2ff97127c76117abb9b3df8