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 CF228584968 for ; Fri, 11 Sep 2026 19:56:08 +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=1789156571; cv=none; b=jFJs4PCF68DQqObx4+CUnDrsyZVYONowbIMU9ZP6n5d+6Uuy5d5et9dGwDm7g5+9NxYEAFiFIjiREx2xce7bj9vJTJwpuIrDJaIdswhZqy1NDOwyVO8YzSCTbkTU2Oz1yb6ErZZGPSQyS/v6bRIeX2SKOZxdDoy1JSU1GSbQY2c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789156571; c=relaxed/simple; bh=Q6DnlPXtGmcL282vkNR1QFCgrAa6DNIp/XdP5Sux/eo=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Y4k1lbyG3nYP4EMsmFQ9T/xKNEDYgZ0NU6YyGknuG8gAtIsQ9k9y4GU6iOeMBAo8i77573blVV1BG/neBaPpt89xo72jjCSqnx/luLeT9y0gaT7M4/Ix3UYLxt2AKdoHvBPFAwj+Y0Xr5Nq9+qkE4ODtVT8HKQ0/KL+fYzLQQPY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=E5cj+P7D; 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="E5cj+P7D" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E53F51F00898; Fri, 11 Sep 2026 19:56:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789156568; bh=WI60Oea0VQHesO7enQldxGs0X3A7QMab8tIHKdtJCmM=; h=From:To:Cc:Subject:Date:Reply-To; b=E5cj+P7Ds6zWxpfSuGRJutgaly0XJStw2EEYjrSxwdfH+tXpP1yp6tNvvnpaNrr2r hz0GyWGnpEQaU16aGzIOypyRfUkqW4vke0XHiDq9/2d3MgnFzh8+vedhU5txyWvQvw 3aXWYZwKsXuh641vbFC/piVruyqXP1IlOXMhq0Y4= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-89561: ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv() Date: Fri, 11 Sep 2026 21:44:10 +0200 Message-ID: <2026091123-CVE-2026-89561-82ab@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=3512; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=MK/GlkSORT48mB/oadrmOlMERzYko20yAeKI55dzHUQ=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlLIpOvr+o+aSC00d7QoCTn1lutFUdSmIQrPmTsWfC3i XnCjKZ7HbEsDIJMDLJiiixftvEc3V9xSNHL0PY0zBxWJpAhDFycAjCRGWcZ5op8W60W0u3bdvhI jucVz13Sakrl2xgWHAmue2yrlHtSdZXQ0d9He7TNd++QBwA= 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: fix NULL dereference of idev in ipv6_rpl_srh_rcv() ipv6_rpl_srh_rcv() dereferences idev from __in6_dev_get() without a NULL check when reading idev->cnf.rpl_seg_enabled. When the device's MTU drops below IPV6_MIN_MTU, addrconf_ifdown() clears dev->ip6_ptr through RCU_INIT_POINTER(). A packet that passed the idev check in ip6_rcv_core() can then reach ipv6_rpl_srh_rcv() with dev->ip6_ptr already NULL. Reproduced by flooding the receiving interface with ping6 traffic while flapping its MTU between 1500 and 1200: BUG: KASAN: null-ptr-deref in ipv6_rpl_srh_rcv+0xb3/0x1070 Read of size 4 at addr 00000000000006b4 by task ping6/394 CPU: 2 UID: 0 PID: 394 Comm: ping6 Not tainted 7.2.0-rc7-micro-vm-dev-00095-g24ef02f934ee #240 PREEMPT(full) Call Trace: kasan_report+0xc6/0x100 ipv6_rpl_srh_rcv+0xb3/0x1070 ip6_protocol_deliver_rcu+0x759/0x9a0 ip6_input_finish+0xa8/0x1b0 ip6_input+0xe1/0x490 ipv6_rcv+0x33d/0x460 __netif_receive_skb_one_core+0xd6/0x130 process_backlog+0x2cc/0xa00 __napi_poll.constprop.0+0x56/0x270 net_rx_action+0x327/0x730 handle_softirqs+0x11e/0x630 do_softirq+0xb3/0xf0 Both ipv6_rpl_srh_rcv() and ipv6_srh_rcv() are called only from ipv6_rthdr_rcv(), which already has an idev lookup. Fix the NULL dereference on the RPL path by checking idev in ipv6_rthdr_rcv(), before it calls either function. The callees take idev as an argument and no longer call __in6_dev_get(), so the packet is now dropped in one place, with SKB_DROP_REASON_IPV6DISABLED on both paths. The Linux kernel CVE team has assigned CVE-2026-89561 to this issue. Affected and fixed versions =========================== Issue introduced in 5.7 with commit 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 and fixed in 6.18.50 with commit 63f50e9f90d0287ad66a0955ebfc2d3a9c044a1c Issue introduced in 5.7 with commit 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 and fixed in 7.2.4 with commit eab3a917cdcb182542a3aac6a0d2d30659ca9821 Issue introduced in 5.7 with commit 8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3 and fixed in 7.3-rc1 with commit f826df95332c07380206dbd54178b6eefb311aba 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-2026-89561 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/63f50e9f90d0287ad66a0955ebfc2d3a9c044a1c https://git.kernel.org/stable/c/eab3a917cdcb182542a3aac6a0d2d30659ca9821 https://git.kernel.org/stable/c/f826df95332c07380206dbd54178b6eefb311aba