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 6AE9F3CF668 for ; Thu, 21 May 2026 12:18:05 +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=1779365886; cv=none; b=Qb+wEQAqW864bGHft7MSuxawou6F3JvCWWMnGNCVsJRR3IUrc+gJ7BIOpbw5wGme/AOkG0cUvGUsJV3gVufEx20qbFh+hDbDQ00LVbkL7SZU2DfuBLKqGHQAHxE4xuZNs1oX+YKlH+RLRXAteBGIyEEy/3rG3YBBDnwiIDv4SwM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779365886; c=relaxed/simple; bh=qXmO+uDLEk1oKhltx7MPzxaUcKS0wOMLmj5w7KxyWEg=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=cxp0CdReN1v1xFhkPjj4RhdzFy8z8sRLtfYAg/+7hPyajFvDtqRGvXApLoBqSDGIXlhRQUj+hgqio5po6mHVohz3Yb2wNHWy7fUD6aKZuPG5wQNnCBaIdcCzqsuG6cZwcoAW8T+INkE1X2kI2Upy+RNnfF6gCj1lDufohVaJZko= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=QmVUsRKW; 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="QmVUsRKW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A5C1C1F000E9; Thu, 21 May 2026 12:18:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1779365885; bh=xajFKDw4vYnGfy6/vo9QrFMf/9h/E+KELQduLXW+kE0=; h=From:To:Cc:Subject:Date:Reply-To; b=QmVUsRKWQwiVIs281rT61Vuop/KEK7u13xuMl9i19AIvYE9FPgQJTMRxj9xgjIBDC +5tJwsi0XrUaMzI/ovWD89VeoQiEYgCWZEaxpWhlgbEdiqXc1tM0cKcq2WwxZCsj8n R3+9Hbl+3fzXTafjL1PGV+pfS80s1Exsb+Co+N1g= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-43501: ipv6: rpl: reserve mac_len headroom when recompressed SRH grows Date: Thu, 21 May 2026 14:18:01 +0200 Message-ID: <2026052159-CVE-2026-43501-63a6@gregkh> X-Mailer: git-send-email 2.54.0 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=3674; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=gmlnO/PhJy66LrbD1KBTbAC/LpKhzU5pX0TmL8LdiV8=; b=owGbwMvMwCRo6H6F97bub03G02pJDFl8378796XPvF7zR+jx4c8nJDWK7264wurzrsv86fkl6 1PuT31xqyOWhUGQiUFWTJHlyzaeo/srDil6GdqehpnDygQyhIGLUwAmUmDEMN97+UWX7g9d/16x aU4uFrX5Yh8gvpRhJuPrqvvmWz8bT1397wKXipIf3y233wA= 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: ipv6: rpl: reserve mac_len headroom when recompressed SRH grows ipv6_rpl_srh_rcv() decompresses an RFC 6554 Source Routing Header, swaps the next segment into ipv6_hdr->daddr, recompresses, then pulls the old header and pushes the new one plus the IPv6 header back. The recompressed header can be larger than the received one when the swap reduces the common-prefix length the segments share with daddr (CmprI=0, CmprE>0, seg[0][0] != daddr[0] gives the maximum +8 bytes). pskb_expand_head() was gated on segments_left == 0, so on earlier segments the push consumed unchecked headroom. Once skb_push() leaves fewer than skb->mac_len bytes in front of data, skb_mac_header_rebuild()'s call to: skb_set_mac_header(skb, -skb->mac_len); will store (data - head) - mac_len into the u16 mac_header field, which wraps to ~65530, and the following memmove() writes mac_len bytes ~64KiB past skb->head. A single AF_INET6/SOCK_RAW/IPV6_HDRINCL packet over lo with a two segment type-3 SRH (CmprI=0, CmprE=15) reaches headroom 8 after one pass; KASAN reports a 14-byte OOB write in ipv6_rthdr_rcv. Fix this by expanding the head whenever the remaining room is less than the push size plus mac_len, and request that much extra so the rebuilt MAC header fits afterwards. The Linux kernel CVE team has assigned CVE-2026-43501 to this issue. Affected and fixed versions =========================== Issue introduced in 5.7 with commit 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 and fixed in 6.6.140 with commit 8e8be63465a5e80394c70324603dfea1bfdad48f Issue introduced in 5.7 with commit 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 and fixed in 6.12.86 with commit 4babc2d9fda2df43823b85d08a0180b68f1b0854 Issue introduced in 5.7 with commit 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 and fixed in 6.18.27 with commit c261d07a80576dc8ccf394ef8f074f8c67a06b37 Issue introduced in 5.7 with commit 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 and fixed in 7.0.4 with commit 7398ebefbfd4f8a31d4f665a4213302fa995494b Issue introduced in 5.7 with commit 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 and fixed in 7.1-rc2 with commit 9e6bf146b55999a095bb14f73a843942456d1adc 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-2026-43501 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/exthdrs.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/8e8be63465a5e80394c70324603dfea1bfdad48f https://git.kernel.org/stable/c/4babc2d9fda2df43823b85d08a0180b68f1b0854 https://git.kernel.org/stable/c/c261d07a80576dc8ccf394ef8f074f8c67a06b37 https://git.kernel.org/stable/c/7398ebefbfd4f8a31d4f665a4213302fa995494b https://git.kernel.org/stable/c/9e6bf146b55999a095bb14f73a843942456d1adc