{"id":"CVE-2025-21999","state":"PUBLISHED","title":"proc: fix UAF in proc_get_inode()","description":"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's inode instantiation.\n\nThe bug is that pde->proc_ops don't 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->proc_ops\nnever changes so information necessary for inode instantiation can be\nsaved _before_ proc_register() in PDE itself and used later, avoiding\npde->proc_ops->...  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->i_sb, de);\n  mod->exit()\n    proc_remove\n      remove_proc_subtree\n       proc_entry_rundown(de);\n  free_module(mod);\n\n                               if (S_ISREG(inode->i_mode))\n\t                         if (de->proc_ops->proc_read_iter)\n                           --> 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 <TASK>\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't do 2 atomic ops on the common path]","publishedAt":"2025-04-03T07:19:03.040Z","updatedAt":"2026-10-15T01:05:17.437Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"97a32539b9568bb653683349e5a76d02ff3c3e2c","status":"affected","lessThan":"eda279586e571b05dff44d48e05f8977ad05855d","versionType":"git"},{"version":"97a32539b9568bb653683349e5a76d02ff3c3e2c","status":"affected","lessThan":"4b0b8445b6fd41e6f62ac90547a0ea9d348de3fa","versionType":"git"},{"version":"97a32539b9568bb653683349e5a76d02ff3c3e2c","status":"affected","lessThan":"966f331403dc3ed04ff64eaf3930cf1267965e53","versionType":"git"},{"version":"97a32539b9568bb653683349e5a76d02ff3c3e2c","status":"affected","lessThan":"63b53198aff2e4e6c5866a4ff73c7891f958ffa4","versionType":"git"},{"version":"97a32539b9568bb653683349e5a76d02ff3c3e2c","status":"affected","lessThan":"ede3e8ac90ae106f0b29cd759aadebc1568f1308","versionType":"git"},{"version":"97a32539b9568bb653683349e5a76d02ff3c3e2c","status":"affected","lessThan":"64dc7c68e040251d9ec6e989acb69f8f6ae4a10b","versionType":"git"},{"version":"97a32539b9568bb653683349e5a76d02ff3c3e2c","status":"affected","lessThan":"654b33ada4ab5e926cd9c570196fefa7bec7c1df","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/proc/generic.c","fs/proc/inode.c","fs/proc/internal.h","include/linux/proc_fs.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.6","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.6","versionType":"semver"},{"version":"5.10.236","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.180","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.132","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.85","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.21","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.13.9","status":"unaffected","lessThanOrEqual":"6.13.*","versionType":"semver"},{"version":"6.14","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/proc/generic.c","fs/proc/inode.c","fs/proc/internal.h","include/linux/proc_fs.h"]}],"references":["https://git.kernel.org/stable/c/eda279586e571b05dff44d48e05f8977ad05855d","https://git.kernel.org/stable/c/4b0b8445b6fd41e6f62ac90547a0ea9d348de3fa","https://git.kernel.org/stable/c/966f331403dc3ed04ff64eaf3930cf1267965e53","https://git.kernel.org/stable/c/63b53198aff2e4e6c5866a4ff73c7891f958ffa4","https://git.kernel.org/stable/c/ede3e8ac90ae106f0b29cd759aadebc1568f1308","https://git.kernel.org/stable/c/64dc7c68e040251d9ec6e989acb69f8f6ae4a10b","https://git.kernel.org/stable/c/654b33ada4ab5e926cd9c570196fefa7bec7c1df","https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html","https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html","https://cert-portal.siemens.com/productcert/html/ssa-019113.html","https://cert-portal.siemens.com/productcert/html/ssa-457936.html"],"weaknesses":["CWE-416"],"ingestedAt":"2026-10-29T20:08:39.238Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/21xxx/CVE-2025-21999.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-21999","state":"PUBLISHED","datePublished":"2025-04-03T07:19:03.040Z","dateUpdated":"2026-10-15T01:05:17.437Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2024-12-29T08:45:45.801Z"},"containers":{"cna":{"title":"proc: fix UAF in proc_get_inode()","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's inode instantiation.\n\nThe bug is that pde->proc_ops don't 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->proc_ops\nnever changes so information necessary for inode instantiation can be\nsaved _before_ proc_register() in PDE itself and used later, avoiding\npde->proc_ops->...  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->i_sb, de);\n  mod->exit()\n    proc_remove\n      remove_proc_subtree\n       proc_entry_rundown(de);\n  free_module(mod);\n\n                               if (S_ISREG(inode->i_mode))\n\t                         if (de->proc_ops->proc_read_iter)\n                           --> 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 <TASK>\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't do 2 atomic ops on the common path]"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"97a32539b9568bb653683349e5a76d02ff3c3e2c","status":"affected","lessThan":"eda279586e571b05dff44d48e05f8977ad05855d","versionType":"git"},{"version":"97a32539b9568bb653683349e5a76d02ff3c3e2c","status":"affected","lessThan":"4b0b8445b6fd41e6f62ac90547a0ea9d348de3fa","versionType":"git"},{"version":"97a32539b9568bb653683349e5a76d02ff3c3e2c","status":"affected","lessThan":"966f331403dc3ed04ff64eaf3930cf1267965e53","versionType":"git"},{"version":"97a32539b9568bb653683349e5a76d02ff3c3e2c","status":"affected","lessThan":"63b53198aff2e4e6c5866a4ff73c7891f958ffa4","versionType":"git"},{"version":"97a32539b9568bb653683349e5a76d02ff3c3e2c","status":"affected","lessThan":"ede3e8ac90ae106f0b29cd759aadebc1568f1308","versionType":"git"},{"version":"97a32539b9568bb653683349e5a76d02ff3c3e2c","status":"affected","lessThan":"64dc7c68e040251d9ec6e989acb69f8f6ae4a10b","versionType":"git"},{"version":"97a32539b9568bb653683349e5a76d02ff3c3e2c","status":"affected","lessThan":"654b33ada4ab5e926cd9c570196fefa7bec7c1df","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/proc/generic.c","fs/proc/inode.c","fs/proc/internal.h","include/linux/proc_fs.h"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.6","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.6","versionType":"semver"},{"version":"5.10.236","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.180","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.132","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.85","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.21","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.13.9","status":"unaffected","lessThanOrEqual":"6.13.*","versionType":"semver"},{"version":"6.14","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/proc/generic.c","fs/proc/inode.c","fs/proc/internal.h","include/linux/proc_fs.h"]}],"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"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The vulnerable path is reached through ordinary local syscalls (stat/open/newstat) on paths under /proc, as shown by the commit's own trace from `ls` via `__do_sys_newstat` → `path_lookupat` → `proc_lookup_de` → `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 — `/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's exploitation loop is entirely self-driven — a continuous stat() loop on the target /proc entry — 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's 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 — \"BUG: unable to handle page fault for address: fffffbfff80a702b … Oops: 0000 [#1] PREEMPT SMP KASAN PTI\" at `proc_get_inode+0x302` — and the attacker can retrigger it at will with a stat() loop, causing kernel crash/denial of service."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T11:55:55.058Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"5.10.236"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"5.15.180"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"6.1.132"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"6.6.85"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"6.12.21"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"6.13.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.6","versionEndExcluding":"6.14"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"cvssV3_1":{"scope":"UNCHANGED","version":"3.1","baseScore":7.8,"attackVector":"LOCAL","baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","integrityImpact":"HIGH","userInteraction":"NONE","attackComplexity":"LOW","availabilityImpact":"HIGH","privilegesRequired":"LOW","confidentialityImpact":"HIGH"}},{"other":{"type":"ssvc","content":{"id":"CVE-2025-21999","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2025-04-03T15:26:31.372538Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-416","lang":"en","type":"CWE","description":"CWE-416 Use After Free"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2025-04-03T15:27:39.157Z"}},{"title":"CVE Program Container","references":[{"url":"https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"},{"url":"https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html"}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2025-11-03T19:40:42.019Z"}},{"affected":[{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIPLUS S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIPLUS S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]}],"references":[{"url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-457936.html"}],"providerMetadata":{"shortName":"siemens-SADP","orgId":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e","dateUpdated":"2026-10-15T01:05:17.437Z"},"x_adpType":"supplier"}]}}}