{"id":"CVE-2026-98959","published":"2026-10-23T13:17:17Z","modified":"2026-10-24T14:16:49Z","title":"In the Linux kernel, the following vulnerability has been resolved: btrfs: fix xattr replace when multiple xattrs are…","vendor":"Linux","product":"Linux","tier":"core","eol":null,"description":{"text":"In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix xattr replace when multiple xattrs are packed in the same item\n\nIf we have a btrfs_dir_item item that packs multiple xattrs and then we\nreplace the value of one of them (with the setxattr(2) family of syscalls)\nwith another value of a different size, we end up not having a fully\ninitialized btrfs_dir_item, resulting in a corruption that the tree\nchecker will detect at extent buffer writeback time.\n\nThis is because in btrfs_setxattr() when we find a btrfs_dir_item with\nmultiple xattrs (due to the crc32c hash of their name being the same)\nwe delete one of the xattr items (btrfs_dir_item) and then insert a new\none, but the deletion and insertion results in shifting existing data in\nthe leaf and therefore when the new value of a xattr has a different size,\nthe new btrfs_dir_item is placed in a leaf section that was not\ninitialized and we only copy the value's data and set the value's length\nin the new btrfs_dir_item, without setting the name, the name's length,\nthe key (which must be all zeroes for xattrs), flags (BTRFS_FT_XATTR) and\ntransaction ID.\n\nThe following script reproduces the issue:\n\n  $ cat test.sh\n  #!/bin/bash\n\n  DEV=/dev/sdi\n  MNT=/mnt/sdi\n\n  mkfs.btrfs -f $DEV\n  mount $DEV $MNT\n\n  touch $MNT/testfile\n\n  # Add two xattrs that, on btrfs, have the same hash (crc32c) for their\n  # name and therefore are packed into the same btrfs_dir_item.\n  setfattr -n user.foobar -v 123 $MNT/testfile\n  setfattr -n user.WvG1c1Td -v qwerty $MNT/testfile\n\n  # Verify the xattrs are present.\n  echo \"xattrs before:\"\n  getfattr --absolute-names --dump $MNT/testfile\n\n  # Now replace the value of the foobar xattr with a significantly larger\n  # value.\n  setfattr -n user.foobar -v abcdefghijklmnopqrstuvwxyz $MNT/testfile\n\n  # Check the xattrs have the expected values.\n  echo \"xattrs after:\"\n  getfattr --absolute-names --dump $MNT/testfile\n\n  umount $MNT\n\nRunning it:\n\n  $ ./test.sh\n  (...)\n  xattrs before:\n  # file: /mnt/sdi/testfile\n  user.WvG1c1Td=\"qwerty\"\n  user.foobar=\"123\"\n\n  xattrs after:\n  # file: /mnt/sdi/testfile\n  user.WvG1c1Td=\"qwerty\"\n\nSo the \"user.foobar\" xattr is missing and there was a transaction abort\nwhen unmounting the fs with the following traces in dmesg:\n\n  $ dmesg\n  [869800.159271] BTRFS warning (device sdi): access to eb bytenr 30474240 len 16384 out of range start 16015 len 25964\n  [869800.159293] ------------[ cut here ]------------\n  [869800.159296] WARNING: fs/btrfs/extent_io.c:4408 at report_eb_range+0x44/0x60 [btrfs], CPU#8: getfattr/2605179\n  [869800.168961] Modules linked in: btrfs dm_thin_pool (...)\n  [869800.190527] CPU: 8 UID: 0 PID: 2605179 Comm: getfattr Tainted: G        W           7.3.0-rc3-btrfs-next-244+ #1 PREEMPT(full)\n  [869800.193726] Tainted: [W]=WARN\n  [869800.194502] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.2-0-gea1b7a073390-prebuilt.qemu.org 04/01/2014\n  [869800.197576] RIP: 0010:report_eb_range+0x44/0x60 [btrfs]\n  [869800.198985] Code: 48 8b 7b 18 (...)\n  [869800.203531] RSP: 0018:ffffce4541937d58 EFLAGS: 00010246\n  [869800.204609] RAX: 0000000000000000 RBX: ffff8dde054b8738 RCX: 0000000000000000\n  [869800.206137] RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffffc04c92a0\n  [869800.207645] RBP: 0000000000003e8f R08: 0000000000000000 R09: 3fffffffffefffff\n  [869800.226175] R10: ffffce4541937a88 R11: 0000000000000003 R12: 000000000000656c\n  [869800.227594] R13: ffff8dde14be800f R14: 000000000000656c R15: 0000000000000069\n  [869800.229097] FS:  00007f59023bb780(0000) GS:ffff8de5788ed000(0000) knlGS:0000000000000000\n  [869800.231137] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n  [869800.232321] CR2: 0000558dc45e6a78 CR3: 0000000765b16004 CR4: 0000000000370ef0\n  [869800.233783] Call Trace:\n  [869800.234330]  <TASK>\n  [869800.234791]  read_extent_buffer+0x4d/0x100 [btrfs]\n  [869800.235898]  btrfs_listxattr+0x199/0x240 [btrfs]\n  [869800.236912]  vfs_listxattr+0x51/0\n---truncated---","provenance":"source","from":"NVD"},"summary":{"text":"In the Linux kernel's btrfs filesystem, the xattr replace logic in btrfs_setxattr() mishandles multiple extended attributes packed into the same btrfs_dir_item when one is resized, leaving the new item only partially initialised. An attacker able to set extended attributes on a btrfs file (for example, a local user with write access to a file on a btrfs filesystem, with no network access required) can trigger the corruption, which causes lost xattrs and filesystem errors or transaction aborts.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-29T07:24:19Z"},"cvss":{"score":9.8,"severity":"CRITICAL","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","provenance":"source","from":"NVD"},"epss":{"score":0.00607,"percentile":0.48999,"date":"2026-10-30","provenance":"source"},"kev":null,"vulncheckKev":null,"exploited":false,"otx":{"pulseCount":6,"pulses":[{"name":"Known_Cve | Oct 31, 2026 | Part 1/3","url":"https://otx.alienvault.com/pulse/6ae4af0017a739f65534f550","created":"2026-10-30"},{"name":"Known_Cve | Oct 30, 2026 | Part 1/2","url":"https://otx.alienvault.com/pulse/6ae35d8e6ee9e838fd042498","created":"2026-10-29"},{"name":"Known_Cve | Oct 29, 2026 | Part 2/3","url":"https://otx.alienvault.com/pulse/6ae20c290cecfbc79bd84822","created":"2026-10-28"},{"name":"Known_Cve | Oct 28, 2026 | Part 2/3","url":"https://otx.alienvault.com/pulse/6ae0ba8e2d29f6aa1bfe6f11","created":"2026-10-27"},{"name":"Known_Cve | Oct 27, 2026 | Part 3/3","url":"https://otx.alienvault.com/pulse/6adf68ca1522e5424ef6b0c7","created":"2026-10-26"},{"name":"Known_Cve | Oct 24, 2026 | Part 3/3","url":"https://otx.alienvault.com/pulse/6adb7421f0eaee440740fbf3","created":"2026-10-23"}],"provenance":"machine"},"cwes":[],"references":[{"url":"https://git.kernel.org/stable/c/5877d7138cc4359d26fd7b010eedfd1b3162348f","tags":[]},{"url":"https://git.kernel.org/stable/c/7a53bb4668b319fc6c8a3ce2c21635125c7d2712","tags":[]},{"url":"https://git.kernel.org/stable/c/858bee1c77857aabcc2327cd32dd8266332de332","tags":[]},{"url":"https://git.kernel.org/stable/c/a97114b9b00ed3d05156f3b2ddbf797296260389","tags":[]},{"url":"https://git.kernel.org/stable/c/c1803697a60f22743aa28ad522f805e92d45e3f0","tags":[]}],"techniques":[],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2026-108753","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-108753","exploited":false,"exploitedSince":null,"provenance":"source"},"exploits":[],"exploitSources":null,"exploitRefs":[],"flow":[],"timeline":[{"date":"2026-10-23","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98959","provenance":"source"}],"speed":{"daysToPublicExploit":null,"firstExploitFrom":null,"daysToKev":null},"priority":{"score":18.6,"factors":[{"name":"In a KEV catalog","points":0.0,"detail":"not listed"},{"name":"Recent KEV listing","points":0.0,"detail":"not listed"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":9.8,"detail":"percentile 0.4900"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":0.0,"detail":"none found"},{"name":"Mentioned in OTX pulses","points":1.92,"detail":"6 pulses"},{"name":"CVSS severity","points":6.86,"detail":"base score 9.8"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]}}