Linux: Use After Free
CVE-2025-37738 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 6aff941cb0f7d0c897c3698ad2e30672709135e3, 76c365fa7e2a8bb85f0190cdb4b8cdc99b2fdce3, f737418b6de31c962c7192777ee4018906975383 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.22% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 6aff941cb0f7d0c897c3698ad2e30672709135e3 or 76c365fa7e2a8bb85f0190cdb4b8cdc99b2fdce3 or f737418b6de31c962c7192777ee4018906975383 or cf9291a3449b04688b81e32621e88de8f4314b54, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.4.293 or 5.10.237 or 5.15.181 or 6.1.135, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | e50e5129f384ae282adebfb561189cdb19b81cee up to, but not including, 6aff941cb0f7d0c897c3698ad2e30672709135e3; e50e5129f384ae282adebfb561189cdb19b81cee up to, but not including, 76c365fa7e2a8bb85f0190cdb4b8cdc99b2fdce3; e50e5129f384ae282adebfb561189cdb19b81cee up to, but not including, f737418b6de31c962c7192777ee4018906975383; e50e5129f384ae282adebfb561189cdb19b81cee up to, but not including, cf9291a3449b04688b81e32621e88de8f4314b54; e50e5129f384ae282adebfb561189cdb19b81cee up to, but not including, 362a90cecd36e8a5c415966d0b75b04a0270e4dd; e50e5129f384ae282adebfb561189cdb19b81cee up to, but not including, eb59cc31b6ea076021d14b04e7faab1636b87d0e; e50e5129f384ae282adebfb561189cdb19b81cee up to, but not including, 3bc6317033f365ce578eb6039445fb66162722fd; e50e5129f384ae282adebfb561189cdb19b81cee up to, but not including, 836e625b03a666cf93ff5be328c8cb30336db872; and 2 more ranges | 6aff941cb0f7d0c897c3698ad2e30672709135e3, 76c365fa7e2a8bb85f0190cdb4b8cdc99b2fdce3, f737418b6de31c962c7192777ee4018906975383, cf9291a3449b04688b81e32621e88de8f4314b54, 362a90cecd36e8a5c415966d0b75b04a0270e4dd, eb59cc31b6ea076021d14b04e7faab1636b87d0e |
| Linux | Linux Kernel | before 5.4.293; 5.5 up to, but not including, 5.10.237; 5.11 up to, but not including, 5.15.181; 5.16 up to, but not including, 6.1.135; 6.2 up to, but not including, 6.6.88; 6.7 up to, but not including, 6.12.24; 6.13 up to, but not including, 6.13.12; 6.14 up to, but not including, 6.14.3 | 5.4.293, 5.10.237, 5.15.181, 6.1.135, 6.6.88, 6.12.24 |
| Debian | Debian Linux | 11.0 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: ext4: ignore xattrs past end Once inside 'ext4_xattr_inode_dec_ref_all' we should ignore xattrs entries past the 'end' entry. This fixes the following KASAN reported issue: ================================================================== BUG: KASAN: slab-use-after-free in ext4_xattr_inode_dec_ref_all+0xb8c/0xe90 Read of size 4 at addr ffff888012c120c4 by task repro/2065 CPU: 1 UID: 0 PID: 2065 Comm: repro Not tainted 6.13.0-rc2+ #11 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x1fd/0x300 ? tcp_gro_dev_warn+0x260/0x260 ? _printk+0xc0/0x100 ? read_lock_is_recursive+0x10/0x10 ? irq_work_queue+0x72/0xf0 ? __virt_addr_valid+0x17b/0x4b0 print_address_description+0x78/0x390 print_report+0x107/0x1f0 ? __virt_addr_valid+0x17b/0x4b0 ? __virt_addr_valid+0x3ff/0x4b0 ? __phys_addr+0xb5/0x160 ? ext4_xattr_inode_dec_ref_all+0xb8c/0xe90 kasan_report+0xcc/0x100 ? ext4_xattr_inode_dec_ref_all+0xb8c/0xe90 ext4_xattr_inode_dec_ref_all+0xb8c/0xe90 ? ext4_xattr_delete_inode+0xd30/0xd30 ? __ext4_journal_ensure_credits+0x5f0/0x5f0 ? __ext4_journal_ensure_credits+0x2b/0x5f0 ? inode_update_timestamps+0x410/0x410 ext4_xattr_delete_inode+0xb64/0xd30 ? ext4_truncate+0xb70/0xdc0 ? ext4_expand_extra_isize_ea+0x1d20/0x1d20 ? __ext4_mark_inode_dirty+0x670/0x670 ? ext4_journal_check_start+0x16f/0x240 ? ext4_inode_is_fast_symlink+0x2f2/0x3a0 ext4_evict_inode+0xc8c/0xff0 ? ext4_inode_is_fast_symlink+0x3a0/0x3a0 ? do_raw_spin_unlock+0x53/0x8a0 ? ext4_inode_is_fast_symlink+0x3a0/0x3a0 evict+0x4ac/0x950 ? proc_nr_inodes+0x310/0x310 ? trace_ext4_drop_inode+0xa2/0x220 ? _raw_spin_unlock+0x1a/0x30 ? iput+0x4cb/0x7e0 do_unlinkat+0x495/0x7c0 ? try_break_deleg+0x120/0x120 ? 0xffffffff81000000 ? __check_object_size+0x15a/0x210 ? strncpy_from_user+0x13e/0x250 ? getname_flags+0x1dc/0x530 __x64_sys_unlinkat+0xc8/0xf0 do_syscall_64+0x65/0x110 entry_SYSCALL_64_after_hwframe+0x67/0x6f RIP: 0033:0x434ffd Code: 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 8 RSP: 002b:00007ffc50fa7b28 EFLAGS: 00000246 ORIG_RAX: 0000000000000107 RAX: ffffffffffffffda RBX: 00007ffc50fa7e18 RCX: 0000000000434ffd RDX: 0000000000000000 RSI: 0000000020000240 RDI: 0000000000000005 RBP: 00007ffc50fa7be0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 00007ffc50fa7e08 R14: 00000000004bbf30 R15: 0000000000000001 </TASK> The buggy address belongs to the object at ffff888012c12000 which belongs to the cache filp of size 360 The buggy address is located 196 bytes inside of freed 360-byte region [ffff888012c12000, ffff888012c12168) The buggy address belongs to the physical page: page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12c12 head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 flags: 0x40(head|node=0|zone=0) page_type: f5(slab) raw: 0000000000000040 ffff888000ad7640 ffffea0000497a00 dead000000000004 raw: 0000000000000000 0000000000100010 00000001f5000000 0000000000000000 head: 0000000000000040 ffff888000ad7640 ffffea0000497a00 dead000000000004 head: 0000000000000000 0000000000100010 00000001f5000000 0000000000000000 head: 0000000000000001 ffffea00004b0481 ffffffffffffffff 0000000000000000 head: 0000000000000002 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff888012c11f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff888012c12000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ffff888012c12080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888012c12100: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc ffff888012c12180: fc fc fc fc fc fc fc fc fc ---truncated---
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/362a90cecd36e8a5c415966d0b75b04a0270e4dd
- git.kernel.org/stable/c/3bc6317033f365ce578eb6039445fb66162722fd
- git.kernel.org/stable/c/6aff941cb0f7d0c897c3698ad2e30672709135e3
- git.kernel.org/stable/c/76c365fa7e2a8bb85f0190cdb4b8cdc99b2fdce3
- git.kernel.org/stable/c/836e625b03a666cf93ff5be328c8cb30336db872
- git.kernel.org/stable/c/c8e008b60492cf6fd31ef127aea6d02fd3d314cd
- git.kernel.org/stable/c/cf9291a3449b04688b81e32621e88de8f4314b54
- git.kernel.org/stable/c/eb59cc31b6ea076021d14b04e7faab1636b87d0e
- git.kernel.org/stable/c/f737418b6de31c962c7192777ee4018906975383
Other references
Recent Use After Free vulnerabilities
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