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      "text": "Important"
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    "category": "csaf_vex",
    "csaf_version": "2.0",
    "distribution": {
      "text": "TuxCare License Agreement",
      "tlp": {
        "label": "WHITE",
        "url": "https://www.first.org/tlp/"
      }
    },
    "lang": "en",
    "notes": [
      {
        "category": "legal_disclaimer",
        "text": "This content is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). If you distribute this content, or a modified version of it, you must provide attribution to Cloud Linux Inc. and provide a link to the original.",
        "title": "Terms of Use"
      }
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    "publisher": {
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      "contact_details": "https://tuxcare.com/contact/",
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      "namespace": "https://tuxcare.com/"
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        "summary": "Canonical URL",
        "url": "https://security.tuxcare.com/csaf/v2/els_os/ubuntu18.04els/vex/2025/cve-2025-21753-els_os-ubuntu18_04els.json"
      }
    ],
    "title": "Security update on CVE-2025-21753",
    "tracking": {
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      "generator": {
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      "id": "CVE-2025-21753-ELS_OS-UBUNTU18.04ELS",
      "initial_release_date": "2025-02-27T00:00:00Z",
      "revision_history": [
        {
          "date": "2025-02-27T00:00:00Z",
          "number": "1",
          "summary": "Initial version"
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        {
          "date": "2025-06-10T09:45:36Z",
          "number": "2",
          "summary": "Official Publication"
        },
        {
          "date": "2025-12-23T22:15:38Z",
          "number": "3",
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      "version": "2"
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  "vulnerabilities": [
    {
      "cve": "CVE-2025-21753",
      "cwe": {
        "id": "CWE-416",
        "name": "Use After Free"
      },
      "notes": [
        {
          "category": "description",
          "text": "In the Linux kernel, the following vulnerability has been resolved:\nbtrfs: fix use-after-free when attempting to join an aborted transaction\nWhen we are trying to join the current transaction and if it's aborted,\nwe read its 'aborted' field after unlocking fs_info->trans_lock and\nwithout holding any extra reference count on it. This means that a\nconcurrent task that is aborting the transaction may free the transaction\nbefore we read its 'aborted' field, leading to a use-after-free.\nFix this by reading the 'aborted' field while holding fs_info->trans_lock\nsince any freeing task must first acquire that lock and set\nfs_info->running_transaction to NULL before freeing the transaction.\nThis was reported by syzbot and Dmitry with the following stack traces\nfrom KASAN:\n==================================================================\nBUG: KASAN: slab-use-after-free in join_transaction+0xd9b/0xda0 fs/btrfs/transaction.c:278\nRead of size 4 at addr ffff888011839024 by task kworker/u4:9/1128\nCPU: 0 UID: 0 PID: 1128 Comm: kworker/u4:9 Not tainted 6.13.0-rc7-syzkaller-00019-gc45323b7560e #0\nHardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014\nWorkqueue: events_unbound btrfs_async_reclaim_data_space\nCall Trace:\n<TASK>\n__dump_stack lib/dump_stack.c:94 [inline]\ndump_stack_lvl+0x241/0x360 lib/dump_stack.c:120\nprint_address_description mm/kasan/report.c:378 [inline]\nprint_report+0x169/0x550 mm/kasan/report.c:489\nkasan_report+0x143/0x180 mm/kasan/report.c:602\njoin_transaction+0xd9b/0xda0 fs/btrfs/transaction.c:278\nstart_transaction+0xaf8/0x1670 fs/btrfs/transaction.c:697\nflush_space+0x448/0xcf0 fs/btrfs/space-info.c:803\nbtrfs_async_reclaim_data_space+0x159/0x510 fs/btrfs/space-info.c:1321\nprocess_one_work kernel/workqueue.c:3236 [inline]\nprocess_scheduled_works+0xa66/0x1840 kernel/workqueue.c:3317\nworker_thread+0x870/0xd30 kernel/workqueue.c:3398\nkthread+0x2f0/0x390 kernel/kthread.c:389\nret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147\nret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244\n</TASK>\nAllocated by task 5315:\nkasan_save_stack mm/kasan/common.c:47 [inline]\nkasan_save_track+0x3f/0x80 mm/kasan/common.c:68\npoison_kmalloc_redzone mm/kasan/common.c:377 [inline]\n__kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:394\nkasan_kmalloc include/linux/kasan.h:260 [inline]\n__kmalloc_cache_noprof+0x243/0x390 mm/slub.c:4329\nkmalloc_noprof include/linux/slab.h:901 [inline]\njoin_transaction+0x144/0xda0 fs/btrfs/transaction.c:308\nstart_transaction+0xaf8/0x1670 fs/btrfs/transaction.c:697\nbtrfs_create_common+0x1b2/0x2e0 fs/btrfs/inode.c:6572\nlookup_open fs/namei.c:3649 [inline]\nopen_last_lookups fs/namei.c:3748 [inline]\npath_openat+0x1c03/0x3590 fs/namei.c:3984\ndo_filp_open+0x27f/0x4e0 fs/namei.c:4014\ndo_sys_openat2+0x13e/0x1d0 fs/open.c:1402\ndo_sys_open fs/open.c:1417 [inline]\n__do_sys_creat fs/open.c:1495 [inline]\n__se_sys_creat fs/open.c:1489 [inline]\n__x64_sys_creat+0x123/0x170 fs/open.c:1489\ndo_syscall_x64 arch/x86/entry/common.c:52 [inline]\ndo_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83\nentry_SYSCALL_64_after_hwframe+0x77/0x7f\nFreed by task 5336:\nkasan_save_stack mm/kasan/common.c:47 [inline]\nkasan_save_track+0x3f/0x80 mm/kasan/common.c:68\nkasan_save_free_info+0x40/0x50 mm/kasan/generic.c:582\npoison_slab_object mm/kasan/common.c:247 [inline]\n__kasan_slab_free+0x59/0x70 mm/kasan/common.c:264\nkasan_slab_free include/linux/kasan.h:233 [inline]\nslab_free_hook mm/slub.c:2353 [inline]\nslab_free mm/slub.c:4613 [inline]\nkfree+0x196/0x430 mm/slub.c:4761\ncleanup_transaction fs/btrfs/transaction.c:2063 [inline]\nbtrfs_commit_transaction+0x2c97/0x3720 fs/btrfs/transaction.c:2598\ninsert_balance_item+0x1284/0x20b0 fs/btrfs/volumes.c:3757\nbtrfs_balance+0x992/\n---truncated---",
          "title": "Vulnerability description"
        },
        {
          "category": "general",
          "text": "The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.",
          "title": "CVSS score applicability"
        }
      ],
      "product_status": {
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      "references": [
        {
          "category": "self",
          "summary": "Canonical URL",
          "url": "https://cve.tuxcare.com/els/cve/CVE-2025-21753"
        }
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      "release_date": "2025-02-27T00:00:00",
      "scores": [
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            "attackVector": "LOCAL",
            "availabilityImpact": "HIGH",
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "NONE",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
            "version": "3.1"
          },
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      "threats": [
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          "details": "High"
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