{ "cveId": "CVE-2026-98980", "url": "https://patchblox.com/security/cve/CVE-2026-98980", "summary": "CVE-2026-98980 is fixed in 19 products on 1 platform, first by DEBIAN-CVE-2026-98980, released October 24, 2026. It is not reported as exploited. Patch Radar priority: High.", "title": "namei: don\u0027t reveal overmounted entries in refwalk", "description": "In the Linux kernel, the following vulnerability has been resolved: namei: don\u0027t reveal overmounted entries in refwalk In rcuwalk the dentry is validated before it is accepted. step_into() step_into() rechecks d_seq and __follow_mount_rcu() rechecks mount_lock. An entry that gets unlinked in between causes the lookup to retry and miss. A refwalk doesn\u0027t do this. lookup_fast() takes a reference on the hashed dentry and simply accepts it. So an unlink that happens after the reference was taken isn\u0027t seen by refwalk. That\u0027s fine for a simple file. We just happened to open it before it was unlinked, no problem. For a mountpoint and specifically a locked mountpoint it very much isn\u0027t. The unlink detaches all mounts and then removes the name. Any refwalk that hasn\u0027t traversed the mounts yet simply reveals the underlying entry. It\u0027s a very narrow window but it can be hit: reads of a covered file in 60 s, 3 walkers, ~15000 unlinks no widening 27 that step \u002B 200 us 3741 See the appended patch for a more reliable reproducer. So check the entry after step_into(). unlink(), rmdir() and rename() mark the dentry with dont_mount() before they detach the mounts and remove the dentry. So a dentry that is marked with DCACHE_CANT_MOUNT and is unhashed by the time its mounts were looked at is a name that was unlinked under the refwalk. DCACHE_CANT_MOUNT is read after the mounts were looked up and it is set before they are detached by detach_mounts(). A refwalk that missed the mounts will see DCACHE_CANT_MOUNT. Plain d_unlinked() is fine. A rename takes the dentry off its hash chain but ___d_drop() leaves d_hash.pprev set. So only __d_drop() and a rename over the dentry unhash it. The only move that flips IS_ROOT splices in a disconnected alias. That doesn\u0027t have DCACHE_CANT_MOUNT set. Add the to step_into_slowpath(). \u0022..\u0022 and LOOKUP_DOWN may legitimately land on an unhashed directory. A refwalk that crossed onto a mount has path.mnt different from nd-\u003Epath.mnt. A dentry that a filesystem dropped on its own (d_invalidate(), d_drop()) doesn\u0027t have the flag set and is treated as before. // SPDX-License-Identifier: GPL-2.0 /* * unlink_covered: unlink a file that is a mountpoint in a detached copy of * its mount, against walkers that open it through that copy. * * A is a tmpfs with the file f1 (content SECRET_F) and the plain file * MARK_A. A\u0027 is an open_tree(OPEN_TREE_CLONE) copy of A with MARK_A bound * on A\u0027/f1, held through an O_PATH fd on its root once the tree fd is * closed. Walkers open f1 through that fd while the driver unlinks A/f1, * where nothing is mounted on it. A walker may read MARK_A or get ENOENT. * A read of SECRET_F is a hit: the name was found after its mount was * gone. The lockless walks use openat2(RESOLVE_CACHED). * * usage: unlink_covered [-t seconds] [-w walkers] */ #ifndef _GNU_SOURCE #define _GNU_SOURCE #endif #include \u003Cerrno.h\u003E #include \u003Cfcntl.h\u003E #include \u003Cpthread.h\u003E #include \u003Cstdatomic.h\u003E #include \u003Cstdio.h\u003E #include \u003Cstdlib.h\u003E #include \u003Cstring.h\u003E #include \u003Cunistd.h\u003E #include \u003Csys/mount.h\u003E #include \u003Csys/stat.h\u003E #include \u003Csys/syscall.h\u003E #include \u003Clinux/openat2.h\u003E #ifndef __NR_open_tree #define __NR_open_tree 428 #endif #ifndef __NR_move_mount #define __NR_move_mount 429 #endif #ifndef __NR_openat2 #define __NR_openat2 437 #endif #ifndef OPEN_TREE_CLONE #define OPEN_TREE_CLONE 1 #endif #ifndef OPEN_TREE_CLOEXEC #define OPEN_TREE_CLOEXEC O_CLOEXEC #endif #ifndef MOVE_MOUNT_F_EMPTY_PATH #define MOVE_MOUNT_F_EMPTY_PATH 0x00000004 #endif #define WORK \u0022/tmp/uc\u0022 #define ADIR WORK \u0022/A\u0022 static int duration = 60, nwalkers = 3; static atomic_int stop, writer_waiting; static pthread_rwlock_t cur_lock = PTHREAD_RWLOCK_INITIALIZER; static int cur_fd = -1;\t\t/* the root of A\u0027, -1 while there is none */ static atomic_long n_unlink, n_walk, n_mark, n_enoent, n_othe ---truncated---", "published": "2026-10-23T13:17:19Z", "severity": "Moderate", "cvss": 8.8, "cvssVector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H", "epss": 0.00175, "epssPercentile": 0.07055, "priority": "High", "priorityTier": 3, "exploited": false, "vendorExploited": false, "disclosed": false, "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-98980", "fixes": [ { "platform": "linux", "product": "bpftool6.12", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "bpftool6.12-debuginfo", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "kernel-livepatch-6.12.113-138.209", "release": "amzn 2023", "fixedVersion": "1:1.0-0.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "kernel6.12", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "kernel6.12-debuginfo", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "kernel6.12-debuginfo-common-aarch64", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "kernel6.12-debuginfo-common-x86_64", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "kernel6.12-devel", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "kernel6.12-headers", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "kernel6.12-modules-extra", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "kernel6.12-modules-extra-common", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "kernel6.12-tools", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "kernel6.12-tools-debuginfo", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "kernel6.12-tools-devel", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "linux", "release": "Debian 13.5 (trixie)", "fixedVersion": "6.12.113-1", "fix": "DEBIAN-CVE-2026-98980", "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-98980", "released": "2026-10-24T13:25:57Z" }, { "platform": "linux", "product": "linux", "release": "Debian 14", "fixedVersion": "7.2.11-1", "fix": "DEBIAN-CVE-2026-98980", "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-98980", "released": "2026-10-24T13:25:57Z" }, { "platform": "linux", "product": "perf6.12", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "perf6.12-debuginfo", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "python3-perf6.12", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" }, { "platform": "linux", "product": "python3-perf6.12-debuginfo", "release": "amzn 2023", "fixedVersion": "1:6.12.113-138.209.amzn2023", "fix": "ALAS2023-2026-3335", "url": "https://patchblox.com/security/fix/linux/alas2023-2026-3335", "released": "2026-11-07T01:06:52Z" } ], "noFixYet": [], "dataAsOf": "2026-11-08T19:12:23Z", "attribution": { "text": "Data: Patchblox Patch Radar", "url": "https://patchblox.com/security/patch-radar", "terms": "https://patchblox.com/security/patch-radar/use-the-data" } }