CVE-2025-21999 (GCVE-0-2025-21999)

Vulnerability from cvelistv5 – Published: 2025-04-03 07:19 – Updated: 2026-08-05 11:55
VLAI
Title
proc: fix UAF in proc_get_inode()
Summary
In the Linux kernel, the following vulnerability has been resolved: proc: fix UAF in proc_get_inode() Fix race between rmmod and /proc/XXX's inode instantiation. The bug is that pde->proc_ops don't belong to /proc, it belongs to a module, therefore dereferencing it after /proc entry has been registered is a bug unless use_pde/unuse_pde() pair has been used. use_pde/unuse_pde can be avoided (2 atomic ops!) because pde->proc_ops never changes so information necessary for inode instantiation can be saved _before_ proc_register() in PDE itself and used later, avoiding pde->proc_ops->... dereference. rmmod lookup sys_delete_module proc_lookup_de pde_get(de); proc_get_inode(dir->i_sb, de); mod->exit() proc_remove remove_proc_subtree proc_entry_rundown(de); free_module(mod); if (S_ISREG(inode->i_mode)) if (de->proc_ops->proc_read_iter) --> As module is already freed, will trigger UAF BUG: unable to handle page fault for address: fffffbfff80a702b PGD 817fc4067 P4D 817fc4067 PUD 817fc0067 PMD 102ef4067 PTE 0 Oops: Oops: 0000 [#1] PREEMPT SMP KASAN PTI CPU: 26 UID: 0 PID: 2667 Comm: ls Tainted: G Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) RIP: 0010:proc_get_inode+0x302/0x6e0 RSP: 0018:ffff88811c837998 EFLAGS: 00010a06 RAX: dffffc0000000000 RBX: ffffffffc0538140 RCX: 0000000000000007 RDX: 1ffffffff80a702b RSI: 0000000000000001 RDI: ffffffffc0538158 RBP: ffff8881299a6000 R08: 0000000067bbe1e5 R09: 1ffff11023906f20 R10: ffffffffb560ca07 R11: ffffffffb2b43a58 R12: ffff888105bb78f0 R13: ffff888100518048 R14: ffff8881299a6004 R15: 0000000000000001 FS: 00007f95b9686840(0000) GS:ffff8883af100000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: fffffbfff80a702b CR3: 0000000117dd2000 CR4: 00000000000006f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> proc_lookup_de+0x11f/0x2e0 __lookup_slow+0x188/0x350 walk_component+0x2ab/0x4f0 path_lookupat+0x120/0x660 filename_lookup+0x1ce/0x560 vfs_statx+0xac/0x150 __do_sys_newstat+0x96/0x110 do_syscall_64+0x5f/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e [adobriyan@gmail.com: don't do 2 atomic ops on the common path]
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator (v2.0.3)
CWE
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 97a32539b9568bb653683349e5a76d02ff3c3e2c , < eda279586e571b05dff44d48e05f8977ad05855d (git)
Affected: 97a32539b9568bb653683349e5a76d02ff3c3e2c , < 4b0b8445b6fd41e6f62ac90547a0ea9d348de3fa (git)
Affected: 97a32539b9568bb653683349e5a76d02ff3c3e2c , < 966f331403dc3ed04ff64eaf3930cf1267965e53 (git)
Affected: 97a32539b9568bb653683349e5a76d02ff3c3e2c , < 63b53198aff2e4e6c5866a4ff73c7891f958ffa4 (git)
Affected: 97a32539b9568bb653683349e5a76d02ff3c3e2c , < ede3e8ac90ae106f0b29cd759aadebc1568f1308 (git)
Affected: 97a32539b9568bb653683349e5a76d02ff3c3e2c , < 64dc7c68e040251d9ec6e989acb69f8f6ae4a10b (git)
Affected: 97a32539b9568bb653683349e5a76d02ff3c3e2c , < 654b33ada4ab5e926cd9c570196fefa7bec7c1df (git)
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Linux Linux Affected: 5.6
Unaffected: 0 , < 5.6 (semver)
Unaffected: 5.10.236 , ≤ 5.10.* (semver)
Unaffected: 5.15.180 , ≤ 5.15.* (semver)
Unaffected: 6.1.132 , ≤ 6.1.* (semver)
Unaffected: 6.6.85 , ≤ 6.6.* (semver)
Unaffected: 6.12.21 , ≤ 6.12.* (semver)
Unaffected: 6.13.9 , ≤ 6.13.* (semver)
Unaffected: 6.14 , ≤ * (original_commit_for_fix)
Create a notification for this product.
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
Create a notification for this product.
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
Create a notification for this product.
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nproc: fix UAF in proc_get_inode()\n\nFix race between rmmod and /proc/XXX\u0027s inode instantiation.\n\nThe bug is that pde-\u003eproc_ops don\u0027t belong to /proc, it belongs to a\nmodule, therefore dereferencing it after /proc entry has been registered\nis a bug unless use_pde/unuse_pde() pair has been used.\n\nuse_pde/unuse_pde can be avoided (2 atomic ops!) because pde-\u003eproc_ops\nnever changes so information necessary for inode instantiation can be\nsaved _before_ proc_register() in PDE itself and used later, avoiding\npde-\u003eproc_ops-\u003e...  dereference.\n\n      rmmod                         lookup\nsys_delete_module\n                         proc_lookup_de\n\t\t\t   pde_get(de);\n\t\t\t   proc_get_inode(dir-\u003ei_sb, de);\n  mod-\u003eexit()\n    proc_remove\n      remove_proc_subtree\n       proc_entry_rundown(de);\n  free_module(mod);\n\n                               if (S_ISREG(inode-\u003ei_mode))\n\t                         if (de-\u003eproc_ops-\u003eproc_read_iter)\n                           --\u003e As module is already freed, will trigger UAF\n\nBUG: unable to handle page fault for address: fffffbfff80a702b\nPGD 817fc4067 P4D 817fc4067 PUD 817fc0067 PMD 102ef4067 PTE 0\nOops: Oops: 0000 [#1] PREEMPT SMP KASAN PTI\nCPU: 26 UID: 0 PID: 2667 Comm: ls Tainted: G\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996)\nRIP: 0010:proc_get_inode+0x302/0x6e0\nRSP: 0018:ffff88811c837998 EFLAGS: 00010a06\nRAX: dffffc0000000000 RBX: ffffffffc0538140 RCX: 0000000000000007\nRDX: 1ffffffff80a702b RSI: 0000000000000001 RDI: ffffffffc0538158\nRBP: ffff8881299a6000 R08: 0000000067bbe1e5 R09: 1ffff11023906f20\nR10: ffffffffb560ca07 R11: ffffffffb2b43a58 R12: ffff888105bb78f0\nR13: ffff888100518048 R14: ffff8881299a6004 R15: 0000000000000001\nFS:  00007f95b9686840(0000) GS:ffff8883af100000(0000) knlGS:0000000000000000\nCS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\nCR2: fffffbfff80a702b CR3: 0000000117dd2000 CR4: 00000000000006f0\nDR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\nDR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\nCall Trace:\n \u003cTASK\u003e\n proc_lookup_de+0x11f/0x2e0\n __lookup_slow+0x188/0x350\n walk_component+0x2ab/0x4f0\n path_lookupat+0x120/0x660\n filename_lookup+0x1ce/0x560\n vfs_statx+0xac/0x150\n __do_sys_newstat+0x96/0x110\n do_syscall_64+0x5f/0x170\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\n[adobriyan@gmail.com: don\u0027t do 2 atomic ops on the common path]"
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              "value": "AV:L - The vulnerable path is reached through ordinary local syscalls (stat/open/newstat) on paths under /proc, as shown by the commit\u0027s own trace from `ls` via `__do_sys_newstat` \u2192 `path_lookupat` \u2192 `proc_lookup_de` \u2192 `proc_get_inode`. No network protocol handling is involved.\nAC:L - The attacker fully controls their side of the race and can hold the window open continuously \u2014 `/proc/net` entries use `proc_net_dentry_ops` whose `.d_revalidate` always returns 0, so every single access re-runs `proc_lookup_de()`/`proc_get_inode()`, and fresh procfs mounts or netns via `unshare -Ur` defeat any dcache caching. On the realistic deployment targets (Android, embedded, automotive) module load/unload cycles are frequent and user-inducible via device/radio state changes, so no condition requires attacker-unattainable luck.\nPR:L - Triggering the vulnerable dereference requires only the ability to look up a path under /proc, which is mode 0555 and open to any unprivileged local user; no capability is checked anywhere on the lookup path. Unprivileged users can additionally use user namespaces to obtain fresh procfs/netns instances and to autoload modules that register `/proc/net` entries.\nUI:N - The attacker\u0027s exploitation loop is entirely self-driven \u2014 a continuous stat() loop on the target /proc entry \u2014 and requires no victim to open a file, mount a filesystem, or otherwise participate.\nS:U - The use-after-free occurs in kernel memory and its consequences are confined to the kernel\u0027s own security authority; there is no crossing of a VM, IOMMU, or sandbox boundary.\nC:H - This is a use-after-free on freed module memory; once the vmalloc/execmem region is reclaimed and re-populated (e.g. by a subsequent module load), the stale read feeds attacker-influenceable data into inode setup, and UAF primitives of this class are leveraged for kernel memory disclosure.\nI:H - The UAF causes the kernel to select `i_fop` based on freed, potentially reallocated memory, yielding a stale-object/type-confusion condition on the instantiated inode; use-after-free on kernel structures is exploitable via heap grooming for control-flow-relevant corruption.\nA:H - The commit documents an unrecoverable oops \u2014 \"BUG: unable to handle page fault for address: fffffbfff80a702b \u2026 Oops: 0000 [#1] PREEMPT SMP KASAN PTI\" at `proc_get_inode+0x302` \u2014 and the attacker can retrigger it at will with a stat() loop, causing kernel crash/denial of service."
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      "status": "final",
      "title": "proc: fix UAF in proc_get_inode()",
      "url": "https://msrc.microsoft.com/csaf/vex/2025/msrc_cve-2025-21999.json",
      "version": "2"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-21999\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-04-03T08:15:15.360\",\"lastModified\":\"2026-07-14T13:17:28.107\",\"vulnStatus\":\"Modified\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nproc: fix UAF in proc_get_inode()\\n\\nFix race between rmmod and /proc/XXX\u0027s inode instantiation.\\n\\nThe bug is that pde-\u003eproc_ops don\u0027t belong to /proc, it belongs to a\\nmodule, therefore dereferencing it after /proc entry has been registered\\nis a bug unless use_pde/unuse_pde() pair has been used.\\n\\nuse_pde/unuse_pde can be avoided (2 atomic ops!) because pde-\u003eproc_ops\\nnever changes so information necessary for inode instantiation can be\\nsaved _before_ proc_register() in PDE itself and used later, avoiding\\npde-\u003eproc_ops-\u003e...  dereference.\\n\\n      rmmod                         lookup\\nsys_delete_module\\n                         proc_lookup_de\\n\\t\\t\\t   pde_get(de);\\n\\t\\t\\t   proc_get_inode(dir-\u003ei_sb, de);\\n  mod-\u003eexit()\\n    proc_remove\\n      remove_proc_subtree\\n       proc_entry_rundown(de);\\n  free_module(mod);\\n\\n                               if (S_ISREG(inode-\u003ei_mode))\\n\\t                         if (de-\u003eproc_ops-\u003eproc_read_iter)\\n                           --\u003e As module is already freed, will trigger UAF\\n\\nBUG: unable to handle page fault for address: fffffbfff80a702b\\nPGD 817fc4067 P4D 817fc4067 PUD 817fc0067 PMD 102ef4067 PTE 0\\nOops: Oops: 0000 [#1] PREEMPT SMP KASAN PTI\\nCPU: 26 UID: 0 PID: 2667 Comm: ls Tainted: G\\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996)\\nRIP: 0010:proc_get_inode+0x302/0x6e0\\nRSP: 0018:ffff88811c837998 EFLAGS: 00010a06\\nRAX: dffffc0000000000 RBX: ffffffffc0538140 RCX: 0000000000000007\\nRDX: 1ffffffff80a702b RSI: 0000000000000001 RDI: ffffffffc0538158\\nRBP: ffff8881299a6000 R08: 0000000067bbe1e5 R09: 1ffff11023906f20\\nR10: ffffffffb560ca07 R11: ffffffffb2b43a58 R12: ffff888105bb78f0\\nR13: ffff888100518048 R14: ffff8881299a6004 R15: 0000000000000001\\nFS:  00007f95b9686840(0000) GS:ffff8883af100000(0000) knlGS:0000000000000000\\nCS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\\nCR2: fffffbfff80a702b CR3: 0000000117dd2000 CR4: 00000000000006f0\\nDR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\\nDR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\\nCall Trace:\\n \u003cTASK\u003e\\n proc_lookup_de+0x11f/0x2e0\\n __lookup_slow+0x188/0x350\\n walk_component+0x2ab/0x4f0\\n path_lookupat+0x120/0x660\\n filename_lookup+0x1ce/0x560\\n vfs_statx+0xac/0x150\\n __do_sys_newstat+0x96/0x110\\n do_syscall_64+0x5f/0x170\\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\\n\\n[adobriyan@gmail.com: don\u0027t do 2 atomic ops on the common path]\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: proc: correcci\u00f3n de UAF en proc_get_inode(). Correcci\u00f3n de la competencia entre rmmod y la instanciaci\u00f3n de inodo de /proc/XXX. El error es que pde-\u0026gt;proc_ops no pertenece a /proc, sino a un m\u00f3dulo; por lo tanto, desreferenciarlo despu\u00e9s de registrar la entrada /proc es un error, a menos que se haya usado el par use_pde/unuse_pde(). Se puede evitar usar_pde/unuse_pde (\u00a12 operaciones at\u00f3micas!) porque pde-\u0026gt;proc_ops nunca cambia, de modo que la informaci\u00f3n necesaria para la instanciaci\u00f3n de inodo se puede guardar _antes_ de proc_register() en el propio PDE y usarse m\u00e1s tarde, evitando la desreferencia de pde-\u0026gt;proc_ops-\u0026gt;... . rmmod lookup sys_delete_module proc_lookup_de pde_get(de); proc_get_inode(dir-\u0026gt;i_sb, de); mod-\u0026gt;exit() proc_remove eliminar_sub\u00e1rbol_proc proc_entry_rundown(de); liberar_m\u00f3dulo(mod); if (S_ISREG(inode-\u0026gt;i_mode)) if (de-\u0026gt;proc_ops-\u0026gt;proc_read_iter) --\u0026gt; Como el m\u00f3dulo ya est\u00e1 liberado, se activar\u00e1 UAF ERROR: no se puede manejar el error de p\u00e1gina para la direcci\u00f3n: fffffbfff80a702b PGD 817fc4067 P4D 817fc4067 PUD 817fc0067 PMD 102ef4067 PTE 0 Oops: Oops: 0000 [#1] PREEMPT SMP KASAN PTI CPU: 26 UID: 0 PID: 2667 Comm: ls Tainted: G Nombre del hardware: QEMU Standard PC (i440FX + PIIX, 1996) RIP: 0010:proc_get_inode+0x302/0x6e0 RSP: 0018:ffff88811c837998 EFLAGS: 00010a06 RAX: dffffc0000000000 RBX: fffffffc0538140 RCX: 0000000000000007 RDX: 1ffffffff80a702b RSI: 0000000000000001 RDI: ffffffffc0538158 RBP: ffff8881299a6000 R08: 0000000067bbe1e5 R09: 1ffff11023906f20 R10: ffffffffb560ca07 R11: ffffffffb2b43a58 R12: ffff888105bb78f0 R13: ffff888100518048 R14: ffff8881299a6004 R15: 0000000000000001 FS: 00007f95b9686840(0000) GS:ffff8883af100000(0000) knlGS:000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: fffffbfff80a702b CR3: 0000000117dd2000 CR4: 00000000000006f0 DR0: 00000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Rastreo de llamadas:  proc_lookup_de+0x11f/0x2e0 __lookup_slow+0x188/0x350 walk_component+0x2ab/0x4f0 path_lookupat+0x120/0x660 filename_lookup+0x1ce/0x560 vfs_statx+0xac/0x150 __do_sys_newstat+0x96/0x110 do_syscall_64+0x5f/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e [adobriyan@gmail.com: no realice 2 operaciones at\u00f3micas en la ruta com\u00fan]\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/proc/generic.c\",\"fs/proc/inode.c\",\"fs/proc/internal.h\",\"include/linux/proc_fs.h\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"97a32539b9568bb653683349e5a76d02ff3c3e2c\",\"lessThan\":\"eda279586e571b05dff44d48e05f8977ad05855d\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"97a32539b9568bb653683349e5a76d02ff3c3e2c\",\"lessThan\":\"4b0b8445b6fd41e6f62ac90547a0ea9d348de3fa\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"97a32539b9568bb653683349e5a76d02ff3c3e2c\",\"lessThan\":\"966f331403dc3ed04ff64eaf3930cf1267965e53\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"97a32539b9568bb653683349e5a76d02ff3c3e2c\",\"lessThan\":\"63b53198aff2e4e6c5866a4ff73c7891f958ffa4\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"97a32539b9568bb653683349e5a76d02ff3c3e2c\",\"lessThan\":\"ede3e8ac90ae106f0b29cd759aadebc1568f1308\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"97a32539b9568bb653683349e5a76d02ff3c3e2c\",\"lessThan\":\"64dc7c68e040251d9ec6e989acb69f8f6ae4a10b\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"97a32539b9568bb653683349e5a76d02ff3c3e2c\",\"lessThan\":\"654b33ada4ab5e926cd9c570196fefa7bec7c1df\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/proc/generic.c\",\"fs/proc/inode.c\",\"fs/proc/internal.h\",\"include/linux/proc_fs.h\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5.6\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"5.6\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.10.236\",\"lessThanOrEqual\":\"5.10.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.15.180\",\"lessThanOrEqual\":\"5.15.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.1.132\",\"lessThanOrEqual\":\"6.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.85\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.21\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.13.9\",\"lessThanOrEqual\":\"6.13.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.14\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]},{\"source\":\"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e\",\"affectedData\":[{\"vendor\":\"Siemens\",\"product\":\"SIMATIC 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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-06-28T11:15:11+00:00",
      "cve": "CVE-2025-21999",
      "id": "CVE-2025-21999",
      "initial_release_date": "2025-04-03T00:00:00+00:00",
      "product_status:fixed": "1092",
      "product_status:known_affected": "22",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: proc: fix UAF in proc_get_inode()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-21999.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-07-25T01:01:27Z",
      "cve": "CVE-2025-21999",
      "id": "CVE-2025-21999",
      "initial_release_date": "2025-04-05T02:24:41Z",
      "product_status:known_affected": "432",
      "product_status:known_not_affected": "99",
      "product_status:recommended": "789",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2025-21999",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2025-21999.json",
      "version": "70"
    },
    "vulnrichment": {
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No network protocol handling is involved.\\nAC:L - The attacker fully controls their side of the race and can hold the window open continuously \\u2014 `/proc/net` entries use `proc_net_dentry_ops` whose `.d_revalidate` always returns 0, so every single access re-runs `proc_lookup_de()`/`proc_get_inode()`, and fresh procfs mounts or netns via `unshare -Ur` defeat any dcache caching. On the realistic deployment targets (Android, embedded, automotive) module load/unload cycles are frequent and user-inducible via device/radio state changes, so no condition requires attacker-unattainable luck.\\nPR:L - Triggering the vulnerable dereference requires only the ability to look up a path under /proc, which is mode 0555 and open to any unprivileged local user; no capability is checked anywhere on the lookup path. Unprivileged users can additionally use user namespaces to obtain fresh procfs/netns instances and to autoload modules that register `/proc/net` entries.\\nUI:N - The attacker\u0027s exploitation loop is entirely self-driven \\u2014 a continuous stat() loop on the target /proc entry \\u2014 and requires no victim to open a file, mount a filesystem, or otherwise participate.\\nS:U - The use-after-free occurs in kernel memory and its consequences are confined to the kernel\u0027s own security authority; there is no crossing of a VM, IOMMU, or sandbox boundary.\\nC:H - This is a use-after-free on freed module memory; once the vmalloc/execmem region is reclaimed and re-populated (e.g. by a subsequent module load), the stale read feeds attacker-influenceable data into inode setup, and UAF primitives of this class are leveraged for kernel memory disclosure.\\nI:H - The UAF causes the kernel to select `i_fop` based on freed, potentially reallocated memory, yielding a stale-object/type-confusion condition on the instantiated inode; use-after-free on kernel structures is exploitable via heap grooming for control-flow-relevant corruption.\\nA:H - The commit documents an unrecoverable oops \\u2014 \\\"BUG: unable to handle page fault for address: fffffbfff80a702b \\u2026 Oops: 0000 [#1] PREEMPT SMP KASAN PTI\\\" at `proc_get_inode+0x302` \\u2014 and the attacker can retrigger it at will with a stat() loop, causing kernel crash/denial of service.\"}]}], \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"97a32539b9568bb653683349e5a76d02ff3c3e2c\", \"lessThan\": \"eda279586e571b05dff44d48e05f8977ad05855d\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"97a32539b9568bb653683349e5a76d02ff3c3e2c\", \"lessThan\": \"4b0b8445b6fd41e6f62ac90547a0ea9d348de3fa\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"97a32539b9568bb653683349e5a76d02ff3c3e2c\", \"lessThan\": \"966f331403dc3ed04ff64eaf3930cf1267965e53\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"97a32539b9568bb653683349e5a76d02ff3c3e2c\", \"lessThan\": \"63b53198aff2e4e6c5866a4ff73c7891f958ffa4\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"97a32539b9568bb653683349e5a76d02ff3c3e2c\", \"lessThan\": \"ede3e8ac90ae106f0b29cd759aadebc1568f1308\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"97a32539b9568bb653683349e5a76d02ff3c3e2c\", \"lessThan\": \"64dc7c68e040251d9ec6e989acb69f8f6ae4a10b\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"97a32539b9568bb653683349e5a76d02ff3c3e2c\", \"lessThan\": \"654b33ada4ab5e926cd9c570196fefa7bec7c1df\", \"versionType\": \"git\"}], \"programFiles\": [\"fs/proc/generic.c\", \"fs/proc/inode.c\", \"fs/proc/internal.h\", \"include/linux/proc_fs.h\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"5.6\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"5.6\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"5.10.236\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"5.15.180\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.15.*\"}, {\"status\": \"unaffected\", \"version\": \"6.1.132\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.1.*\"}, {\"status\": \"unaffected\", \"version\": \"6.6.85\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.6.*\"}, {\"status\": \"unaffected\", \"version\": \"6.12.21\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.12.*\"}, {\"status\": \"unaffected\", \"version\": \"6.13.9\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.13.*\"}, {\"status\": \"unaffected\", \"version\": \"6.14\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"fs/proc/generic.c\", \"fs/proc/inode.c\", \"fs/proc/internal.h\", \"include/linux/proc_fs.h\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/eda279586e571b05dff44d48e05f8977ad05855d\"}, {\"url\": \"https://git.kernel.org/stable/c/4b0b8445b6fd41e6f62ac90547a0ea9d348de3fa\"}, {\"url\": \"https://git.kernel.org/stable/c/966f331403dc3ed04ff64eaf3930cf1267965e53\"}, {\"url\": \"https://git.kernel.org/stable/c/63b53198aff2e4e6c5866a4ff73c7891f958ffa4\"}, {\"url\": \"https://git.kernel.org/stable/c/ede3e8ac90ae106f0b29cd759aadebc1568f1308\"}, {\"url\": \"https://git.kernel.org/stable/c/64dc7c68e040251d9ec6e989acb69f8f6ae4a10b\"}, {\"url\": \"https://git.kernel.org/stable/c/654b33ada4ab5e926cd9c570196fefa7bec7c1df\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nproc: fix UAF in proc_get_inode()\\n\\nFix race between rmmod and /proc/XXX\u0027s inode instantiation.\\n\\nThe bug is that pde-\u003eproc_ops don\u0027t belong to /proc, it belongs to a\\nmodule, therefore dereferencing it after /proc entry has been registered\\nis a bug unless use_pde/unuse_pde() pair has been used.\\n\\nuse_pde/unuse_pde can be avoided (2 atomic ops!) because pde-\u003eproc_ops\\nnever changes so information necessary for inode instantiation can be\\nsaved _before_ proc_register() in PDE itself and used later, avoiding\\npde-\u003eproc_ops-\u003e...  dereference.\\n\\n      rmmod                         lookup\\nsys_delete_module\\n                         proc_lookup_de\\n\\t\\t\\t   pde_get(de);\\n\\t\\t\\t   proc_get_inode(dir-\u003ei_sb, de);\\n  mod-\u003eexit()\\n    proc_remove\\n      remove_proc_subtree\\n       proc_entry_rundown(de);\\n  free_module(mod);\\n\\n                               if (S_ISREG(inode-\u003ei_mode))\\n\\t                         if (de-\u003eproc_ops-\u003eproc_read_iter)\\n                           --\u003e As module is already freed, will trigger UAF\\n\\nBUG: unable to handle page fault for address: fffffbfff80a702b\\nPGD 817fc4067 P4D 817fc4067 PUD 817fc0067 PMD 102ef4067 PTE 0\\nOops: Oops: 0000 [#1] PREEMPT SMP KASAN PTI\\nCPU: 26 UID: 0 PID: 2667 Comm: ls Tainted: G\\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996)\\nRIP: 0010:proc_get_inode+0x302/0x6e0\\nRSP: 0018:ffff88811c837998 EFLAGS: 00010a06\\nRAX: dffffc0000000000 RBX: ffffffffc0538140 RCX: 0000000000000007\\nRDX: 1ffffffff80a702b RSI: 0000000000000001 RDI: ffffffffc0538158\\nRBP: ffff8881299a6000 R08: 0000000067bbe1e5 R09: 1ffff11023906f20\\nR10: ffffffffb560ca07 R11: ffffffffb2b43a58 R12: ffff888105bb78f0\\nR13: ffff888100518048 R14: ffff8881299a6004 R15: 0000000000000001\\nFS:  00007f95b9686840(0000) GS:ffff8883af100000(0000) knlGS:0000000000000000\\nCS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\\nCR2: fffffbfff80a702b CR3: 0000000117dd2000 CR4: 00000000000006f0\\nDR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\\nDR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\\nCall Trace:\\n \u003cTASK\u003e\\n proc_lookup_de+0x11f/0x2e0\\n __lookup_slow+0x188/0x350\\n walk_component+0x2ab/0x4f0\\n path_lookupat+0x120/0x660\\n filename_lookup+0x1ce/0x560\\n vfs_statx+0xac/0x150\\n __do_sys_newstat+0x96/0x110\\n do_syscall_64+0x5f/0x170\\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\\n\\n[adobriyan@gmail.com: don\u0027t do 2 atomic ops on the common path]\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.236\", \"versionStartIncluding\": \"5.6\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.180\", \"versionStartIncluding\": \"5.6\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.1.132\", \"versionStartIncluding\": \"5.6\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.6.85\", \"versionStartIncluding\": \"5.6\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.12.21\", \"versionStartIncluding\": \"5.6\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.13.9\", \"versionStartIncluding\": \"5.6\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.14\", \"versionStartIncluding\": \"5.6\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-08-05T11:55:55.058Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2025-21999\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-05T11:55:55.058Z\", \"dateReserved\": \"2024-12-29T08:45:45.801Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2025-04-03T07:19:03.040Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.