Linux: Use After Free
CVE-2024-50047 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 8f14a476abba13144df5434871a7225fd29af633, ef51c0d544b1518b35364480317ab6d3468f205d, bce966530fd5542bbb422cb45ecb775f7a1a6bc3 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 0.52% 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 8f14a476abba13144df5434871a7225fd29af633 or ef51c0d544b1518b35364480317ab6d3468f205d or bce966530fd5542bbb422cb45ecb775f7a1a6bc3 or 0809fb86ad13b29e1d6d491364fc7ea4fb545995, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.57 or 6.11.4, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 35cf94a397280b9e27576ac1480f631bdd3e7b70 up to, but not including, 8f14a476abba13144df5434871a7225fd29af633; 35cf94a397280b9e27576ac1480f631bdd3e7b70 up to, but not including, ef51c0d544b1518b35364480317ab6d3468f205d; 35cf94a397280b9e27576ac1480f631bdd3e7b70 up to, but not including, bce966530fd5542bbb422cb45ecb775f7a1a6bc3; 35cf94a397280b9e27576ac1480f631bdd3e7b70 up to, but not including, 0809fb86ad13b29e1d6d491364fc7ea4fb545995; 35cf94a397280b9e27576ac1480f631bdd3e7b70 up to, but not including, 538c26d9bf70c90edc460d18c81008a4e555925a; 35cf94a397280b9e27576ac1480f631bdd3e7b70 up to, but not including, b0abcd65ec545701b8793e12bc27dc98042b151a; 5.4 | 8f14a476abba13144df5434871a7225fd29af633, ef51c0d544b1518b35364480317ab6d3468f205d, bce966530fd5542bbb422cb45ecb775f7a1a6bc3, 0809fb86ad13b29e1d6d491364fc7ea4fb545995, 538c26d9bf70c90edc460d18c81008a4e555925a, b0abcd65ec545701b8793e12bc27dc98042b151a |
| Linux | Linux Kernel | before 6.6.57; 6.7 up to, but not including, 6.11.4 | 6.6.57, 6.11.4 |
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 | 9.8 | Critical | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: smb: client: fix UAF in async decryption Doing an async decryption (large read) crashes with a slab-use-after-free way down in the crypto API. Reproducer: # mount.cifs -o ...,seal,esize=1 //srv/share /mnt # dd if=/mnt/largefile of=/dev/null ... [ 194.196391] ================================================================== [ 194.196844] BUG: KASAN: slab-use-after-free in gf128mul_4k_lle+0xc1/0x110 [ 194.197269] Read of size 8 at addr ffff888112bd0448 by task kworker/u77:2/899 [ 194.197707] [ 194.197818] CPU: 12 UID: 0 PID: 899 Comm: kworker/u77:2 Not tainted 6.11.0-lku-00028-gfca3ca14a17a-dirty #43 [ 194.198400] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.2-3-gd478f380-prebuilt.qemu.org 04/01/2014 [ 194.199046] Workqueue: smb3decryptd smb2_decrypt_offload [cifs] [ 194.200032] Call Trace: [ 194.200191] <TASK> [ 194.200327] dump_stack_lvl+0x4e/0x70 [ 194.200558] ? gf128mul_4k_lle+0xc1/0x110 [ 194.200809] print_report+0x174/0x505 [ 194.201040] ? __pfx__raw_spin_lock_irqsave+0x10/0x10 [ 194.201352] ? srso_return_thunk+0x5/0x5f [ 194.201604] ? __virt_addr_valid+0xdf/0x1c0 [ 194.201868] ? gf128mul_4k_lle+0xc1/0x110 [ 194.202128] kasan_report+0xc8/0x150 [ 194.202361] ? gf128mul_4k_lle+0xc1/0x110 [ 194.202616] gf128mul_4k_lle+0xc1/0x110 [ 194.202863] ghash_update+0x184/0x210 [ 194.203103] shash_ahash_update+0x184/0x2a0 [ 194.203377] ? __pfx_shash_ahash_update+0x10/0x10 [ 194.203651] ? srso_return_thunk+0x5/0x5f [ 194.203877] ? crypto_gcm_init_common+0x1ba/0x340 [ 194.204142] gcm_hash_assoc_remain_continue+0x10a/0x140 [ 194.204434] crypt_message+0xec1/0x10a0 [cifs] [ 194.206489] ? __pfx_crypt_message+0x10/0x10 [cifs] [ 194.208507] ? srso_return_thunk+0x5/0x5f [ 194.209205] ? srso_return_thunk+0x5/0x5f [ 194.209925] ? srso_return_thunk+0x5/0x5f [ 194.210443] ? srso_return_thunk+0x5/0x5f [ 194.211037] decrypt_raw_data+0x15f/0x250 [cifs] [ 194.212906] ? __pfx_decrypt_raw_data+0x10/0x10 [cifs] [ 194.214670] ? srso_return_thunk+0x5/0x5f [ 194.215193] smb2_decrypt_offload+0x12a/0x6c0 [cifs] This is because TFM is being used in parallel. Fix this by allocating a new AEAD TFM for async decryption, but keep the existing one for synchronous READ cases (similar to what is done in smb3_calc_signature()). Also remove the calls to aead_request_set_callback() and crypto_wait_req() since it's always going to be a synchronous operation.
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: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other references
- git.kernel.org/stable/c/8f14a476abba13144df5434871a7225fd29af633
- git.kernel.org/stable/c/bce966530fd5542bbb422cb45ecb775f7a1a6bc3
- git.kernel.org/stable/c/ef51c0d544b1518b35364480317ab6d3468f205d
- lists.debian.org/debian-lts-announce/2025/03/msg00001.html
- lists.debian.org/debian-lts-announce/2025/05/msg00030.html
Recent Use After Free vulnerabilities
- 7.0 High severity
- 7.0 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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