CVE-2025-21999: Linux kernel · proc: fix UAF in proc_get_inode()
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.8 High · fixed in 5.15.0-1086.93~20.04.1 : patch Linux kernel soon.
Data as of 28 Oct 2026, 11:14 UTC
- Patch
- Available – fixed in 5.15.0-1086.93~20.04.1, 5.15.0-1091.100~20.04.1, 5.15.0-1085.94~20.04.1 +64
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 3 Apr 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Patches and advisories
- ubuntu.com/security/notices/USN-7591-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7591-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7591-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7592-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7593-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7591-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7597-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7597-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7598-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7602-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7605-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7606-1 (opens in a new tab)
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 24.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-6.11pkg:deb/ubuntu/linux-azure-6.11?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-nvidiapkg:deb/ubuntu/linux-azure-nvidia?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
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]
References
- ubuntu.com/security/CVE-2025-21999 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2025-21999 (opens in a new tab)
- git.kernel.org/linus/654b33ada4ab5e926cd9c570196fefa7bec7c1df (opens in a new tab)
- git.kernel.org/stable/c/63b53198aff2e4e6c5866a4ff73c7891f958ffa4 (opens in a new tab)
- git.kernel.org/stable/c/64dc7c68e040251d9ec6e989acb69f8f6ae4a10b (opens in a new tab)
- git.kernel.org/stable/c/654b33ada4ab5e926cd9c570196fefa7bec7c1df (opens in a new tab)
- git.kernel.org/stable/c/966f331403dc3ed04ff64eaf3930cf1267965e53 (opens in a new tab)
- git.kernel.org/stable/c/ede3e8ac90ae106f0b29cd759aadebc1568f1308 (opens in a new tab)
- ubuntu.com/security/notices/USN-7591-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7591-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7591-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7592-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7593-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7591-4 (opens in a new tab)
- ubuntu.com/security/notices/USN-7597-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7597-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7598-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7602-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7605-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7606-1 (opens in a new tab)