Linux: Use After Free
CVE-2024-56581 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 dfb9fe7de61f34cc241ab3900bdde93341096e0e, 6fd018aa168e472ce35be32296d109db6adb87ea, d2b85ce0561fde894e28fa01bd5d32820d585006 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 0.24% 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 dfb9fe7de61f34cc241ab3900bdde93341096e0e or 6fd018aa168e472ce35be32296d109db6adb87ea or d2b85ce0561fde894e28fa01bd5d32820d585006 or 6370db28af9a8ae3bbdfe97f8a48f8f995e144cf, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.4.287 or 5.10.231 or 5.15.174 or 6.1.120, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | fd708b81d972a0714b02a60eb4792fdbf15868c4 up to, but not including, dfb9fe7de61f34cc241ab3900bdde93341096e0e; fd708b81d972a0714b02a60eb4792fdbf15868c4 up to, but not including, 6fd018aa168e472ce35be32296d109db6adb87ea; fd708b81d972a0714b02a60eb4792fdbf15868c4 up to, but not including, d2b85ce0561fde894e28fa01bd5d32820d585006; fd708b81d972a0714b02a60eb4792fdbf15868c4 up to, but not including, 6370db28af9a8ae3bbdfe97f8a48f8f995e144cf; fd708b81d972a0714b02a60eb4792fdbf15868c4 up to, but not including, 4275ac2741941c9c7c2293619fdbacb9f70ba85b; fd708b81d972a0714b02a60eb4792fdbf15868c4 up to, but not including, a6f9e7a0bf1185c9070c0de03bb85eafb9abd650; fd708b81d972a0714b02a60eb4792fdbf15868c4 up to, but not including, 7c4e39f9d2af4abaf82ca0e315d1fd340456620f; 4.15 | dfb9fe7de61f34cc241ab3900bdde93341096e0e, 6fd018aa168e472ce35be32296d109db6adb87ea, d2b85ce0561fde894e28fa01bd5d32820d585006, 6370db28af9a8ae3bbdfe97f8a48f8f995e144cf, 4275ac2741941c9c7c2293619fdbacb9f70ba85b, a6f9e7a0bf1185c9070c0de03bb85eafb9abd650 |
| Linux | Linux Kernel | 4.15 up to, but not including, 5.4.287; 5.5 up to, but not including, 5.10.231; 5.11 up to, but not including, 5.15.174; 5.16 up to, but not including, 6.1.120; 6.2 up to, but not including, 6.6.64; 6.7 up to, but not including, 6.12.4; 6.13 | 5.4.287, 5.10.231, 5.15.174, 6.1.120, 6.6.64, 6.12.4 |
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 | 7.0 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
| CVSS 3.1 | 7.8 | High | CISA (ADP) |
Official description
In the Linux kernel, the following vulnerability has been resolved: btrfs: ref-verify: fix use-after-free after invalid ref action At btrfs_ref_tree_mod() after we successfully inserted the new ref entry (local variable 'ref') into the respective block entry's rbtree (local variable 'be'), if we find an unexpected action of BTRFS_DROP_DELAYED_REF, we error out and free the ref entry without removing it from the block entry's rbtree. Then in the error path of btrfs_ref_tree_mod() we call btrfs_free_ref_cache(), which iterates over all block entries and then calls free_block_entry() for each one, and there we will trigger a use-after-free when we are called against the block entry to which we added the freed ref entry to its rbtree, since the rbtree still points to the block entry, as we didn't remove it from the rbtree before freeing it in the error path at btrfs_ref_tree_mod(). Fix this by removing the new ref entry from the rbtree before freeing it. Syzbot report this with the following stack traces: BTRFS error (device loop0 state EA): Ref action 2, root 5, ref_root 0, parent 8564736, owner 0, offset 0, num_refs 18446744073709551615 __btrfs_mod_ref+0x7dd/0xac0 fs/btrfs/extent-tree.c:2523 update_ref_for_cow+0x9cd/0x11f0 fs/btrfs/ctree.c:512 btrfs_force_cow_block+0x9f6/0x1da0 fs/btrfs/ctree.c:594 btrfs_cow_block+0x35e/0xa40 fs/btrfs/ctree.c:754 btrfs_search_slot+0xbdd/0x30d0 fs/btrfs/ctree.c:2116 btrfs_insert_empty_items+0x9c/0x1a0 fs/btrfs/ctree.c:4314 btrfs_insert_empty_item fs/btrfs/ctree.h:669 [inline] btrfs_insert_orphan_item+0x1f1/0x320 fs/btrfs/orphan.c:23 btrfs_orphan_add+0x6d/0x1a0 fs/btrfs/inode.c:3482 btrfs_unlink+0x267/0x350 fs/btrfs/inode.c:4293 vfs_unlink+0x365/0x650 fs/namei.c:4469 do_unlinkat+0x4ae/0x830 fs/namei.c:4533 __do_sys_unlinkat fs/namei.c:4576 [inline] __se_sys_unlinkat fs/namei.c:4569 [inline] __x64_sys_unlinkat+0xcc/0xf0 fs/namei.c:4569 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f BTRFS error (device loop0 state EA): Ref action 1, root 5, ref_root 5, parent 0, owner 260, offset 0, num_refs 1 __btrfs_mod_ref+0x76b/0xac0 fs/btrfs/extent-tree.c:2521 update_ref_for_cow+0x96a/0x11f0 btrfs_force_cow_block+0x9f6/0x1da0 fs/btrfs/ctree.c:594 btrfs_cow_block+0x35e/0xa40 fs/btrfs/ctree.c:754 btrfs_search_slot+0xbdd/0x30d0 fs/btrfs/ctree.c:2116 btrfs_lookup_inode+0xdc/0x480 fs/btrfs/inode-item.c:411 __btrfs_update_delayed_inode+0x1e7/0xb90 fs/btrfs/delayed-inode.c:1030 btrfs_update_delayed_inode fs/btrfs/delayed-inode.c:1114 [inline] __btrfs_commit_inode_delayed_items+0x2318/0x24a0 fs/btrfs/delayed-inode.c:1137 __btrfs_run_delayed_items+0x213/0x490 fs/btrfs/delayed-inode.c:1171 btrfs_commit_transaction+0x8a8/0x3740 fs/btrfs/transaction.c:2313 prepare_to_relocate+0x3c4/0x4c0 fs/btrfs/relocation.c:3586 relocate_block_group+0x16c/0xd40 fs/btrfs/relocation.c:3611 btrfs_relocate_block_group+0x77d/0xd90 fs/btrfs/relocation.c:4081 btrfs_relocate_chunk+0x12c/0x3b0 fs/btrfs/volumes.c:3377 __btrfs_balance+0x1b0f/0x26b0 fs/btrfs/volumes.c:4161 btrfs_balance+0xbdc/0x10c0 fs/btrfs/volumes.c:4538 BTRFS error (device loop0 state EA): Ref action 2, root 5, ref_root 0, parent 8564736, owner 0, offset 0, num_refs 18446744073709551615 __btrfs_mod_ref+0x7dd/0xac0 fs/btrfs/extent-tree.c:2523 update_ref_for_cow+0x9cd/0x11f0 fs/btrfs/ctree.c:512 btrfs_force_cow_block+0x9f6/0x1da0 fs/btrfs/ctree.c:594 btrfs_cow_block+0x35e/0xa40 fs/btrfs/ctree.c:754 btrfs_search_slot+0xbdd/0x30d0 fs/btrfs/ctree.c:2116 btrfs_lookup_inode+0xdc/0x480 fs/btrfs/inode-item.c:411 __btrfs_update_delayed_inode+0x1e7/0xb90 fs/btrfs/delayed-inode.c:1030 btrfs_update_delayed_i ---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/4275ac2741941c9c7c2293619fdbacb9f70ba85b
- git.kernel.org/stable/c/6370db28af9a8ae3bbdfe97f8a48f8f995e144cf
- git.kernel.org/stable/c/6fd018aa168e472ce35be32296d109db6adb87ea
- git.kernel.org/stable/c/7c4e39f9d2af4abaf82ca0e315d1fd340456620f
- git.kernel.org/stable/c/a6f9e7a0bf1185c9070c0de03bb85eafb9abd650
- git.kernel.org/stable/c/d2b85ce0561fde894e28fa01bd5d32820d585006
- git.kernel.org/stable/c/dfb9fe7de61f34cc241ab3900bdde93341096e0e
Other references
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