From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792758625; b=v0425Sjg+z033jfioZaVBvgTqxjz2gqk+k1vUf700ImcnWEuB3X1tQkatz2cuFaiQ/Kb RA2TGa6stU7TYxDHj1xE6IsvRSfI9kNEPNeMWQH1wc9KxerLbiYh9LPk6JR1T3n858cFt eflfto5zooTKXye07BYtyEDGtcXWsRnxxYYUi3OMnV6CFmpvMnkjQiO0ym35rrVcvJFh2 uTgMMSrlC/ioeUDVgXJwqZgs2QxoFE/iqnvwxRdWj4aswDXnkqCfZ2hED0+QercQX3LOz of47pH4JDEkeqbfOwNhww56VMHHdUIPSbvrEay7OsOJp9FBjVu+rztt67FA201bfJRA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792758625; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: Reply-To:MIME-Version:Lines:X-Developer-Signature:X-Developer-Key: Content-Transfer-Encoding; bh=0mtywL1qkaPRv8o30N6r1ZEQxsUDg6LOiDX0o/7bLhA=; b=yh3kcSvjFzqX97fp6oHQvkyTLQAbUDH2XHhGIuonVW5ZUQRqjSieul3UIkhKtFjFsgm5 FuTZuZbYd/cKsbfmwrjrip9XyXtA4NScrsZeywnW7Fq7yKUU21yU5Cua7zM3bFq1WoJed MZSHFuCqbMNAuTpTHoagxvAVaAdB8imi3+iSG0YW9TG/GwqfTdnoeyJsKWFYkDX4zFBCu ljUnq4/7lJOlDurogqBoqSWO6WxVwtFVtF3Rgv8dLzb7ZcQeXkeK0GWORLh+InqyOXnzA gd12R6o0Q+psWo+5SOG5Q+/n82hDfVuATSlbl5eg/mFv+ydX9pxC8dYoJWIMbtJS/LQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=fENXkbY3; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A8275606A31F for ; Fri, 23 Oct 2026 12:30:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=fENXkbY3 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4A4281F01825; Fri, 23 Oct 2026 12:30:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792758624; bh=0mtywL1qkaPRv8o30N6r1ZEQxsUDg6LOiDX0o/7bLhA=; h=From:To:Cc:Subject:Date:Reply-To; b=fENXkbY3NNQOis2DOwBGBBmxGahvQG82HpdEogKLYBDT99nA7XJM/3/o5Zc4GijyV 2c+Iqzd6c88s1s3WNySotxa9Aq7lCmn3rXkWqM/Ty9tIA6IwXCTdQHtNgONvq/dZcj nIdioUwrIwrpRKEEtIB5HhHeFqsyDdBxs4EQqLq4= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-98988: namespace: keep covered mounts covered in OPEN_TREE_NAMESPACE Date: Fri, 23 Oct 2026 14:19:50 +0200 Message-ID: <2026102315-CVE-2026-98988-e980@gregkh> X-Mailer: git-send-email 2.56.0 Reply-To: , X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3631; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=g19tHBqr9mr/Z0QsI5fA+Q7uhBQGu6SHpz94yOzLz1A=; b=owGbwMvMwCRo6H6F97bub03G02pJDFm3Aw4fqxS8Mi/Y9o1z1OFd73P+T2CyWcyz1Cvx7vrXU zepBjK87IhlYRBkYpAVU2T5so3n6P6KQ4pehranYeawMoEMYeDiFICJXKthWLCp5wr33C1lj6fz JrLv8NHf2cla9Ixhwf4V/ex3hTsUffYc6D91X8FjxeW+awA= 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: namespace: keep covered mounts covered in OPEN_TREE_NAMESPACE open_tree(OPEN_TREE_NAMESPACE) creates a new mount namespace from a copy of the tree at the given path. The caller needs to be privileged over its current user namespace because the new mount namespace will be owned by it. It doesn't need to be privileged over the mount namespace the tree is copied from. An unprivileged user just needs to create a user namespace first. The copy follows the rules of a detached bind mount. Without AT_RECURSIVE only the mount itself is cloned and its children are left out. With AT_RECURSIVE unbindable mounts are skipped. Both is fine when the caller has privileges over the source mount namespace because it could unmount those mounts anyway. Not so for an unprivileged user in that mount namespace. For them a mount namespace copy is what unshare() does. copy_mnt_ns() copies everything including unbindable mounts and lock_mnt_tree() makes sure nothing can be unmounted in the copy. Nothing that was covered gets revealed. create_new_namespace() only does the locking and so the covered content is right there in the new mount namespace: # mount -t tmpfs none /tmp/otn; mkdir /tmp/otn/covered # echo hidden > /tmp/otn/covered/under.txt # mount -t tmpfs none /tmp/otn/covered uid 1000, after unshare(CLONE_NEWUSER): fd = open_tree(AT_FDCWD, "/tmp/otn", OPEN_TREE_NAMESPACE); setns(fd, CLONE_NEWNS); open("/covered/under.txt", O_RDONLY) -> "hidden" Covering paths with mounts is how container runtimes mask parts of /proc and /sys and how admins hide things. When the caller's user namespace doesn't own the source mount namespace copy the way unshare() does and refuse a non-recursive copy of a mount that has anything mounted below the requested directory and copy unbindable mounts in a recursive copy. A caller that is privileged over the source mount namespace sees no change. The Linux kernel CVE team has assigned CVE-2026-98988 to this issue. Affected and fixed versions =========================== Issue introduced in 7.0 with commit 9b8a0ba68246a61d903ce62c35c303b1501df28b and fixed in 7.2.11 with commit b8a94a405ddcf45e9470789e0a821d8f2aa4ca10 Issue introduced in 7.0 with commit 9b8a0ba68246a61d903ce62c35c303b1501df28b and fixed in 7.3 with commit 0febe278ec45b1ccdbe9bd5ff1ba365d8fd55e2a 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-2026-98988 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: fs/namespace.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/b8a94a405ddcf45e9470789e0a821d8f2aa4ca10 https://git.kernel.org/stable/c/0febe278ec45b1ccdbe9bd5ff1ba365d8fd55e2a