Linux: Use After Free
CVE-2024-26957 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 7e500849fa558879a1cde43f80c7c048c2437058, 9daddee03de3f231012014dab8ab2b277a116a55, 6470078ab3d8f222115e11c4ec67351f3031b3dd 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 7e500849fa558879a1cde43f80c7c048c2437058 or 9daddee03de3f231012014dab8ab2b277a116a55 or 6470078ab3d8f222115e11c4ec67351f3031b3dd or a55677878b93e9ebc31f66d0e2fb93be5e7836a6, whichever matches your release line, or a later version.
- Update linux_kernel to 7e500849fa55 or 9daddee03de3 or 6470078ab3d8 or a55677878b93, whichever matches your release line, or a later version.
- Update SIMATIC S7-1500 CPU 1518-4 PN/DP MFP to V3.1.5 or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | e28d2af43614eb86f59812e7221735fc221bbc10 up to, but not including, 7e500849fa558879a1cde43f80c7c048c2437058; e28d2af43614eb86f59812e7221735fc221bbc10 up to, but not including, 9daddee03de3f231012014dab8ab2b277a116a55; e28d2af43614eb86f59812e7221735fc221bbc10 up to, but not including, 6470078ab3d8f222115e11c4ec67351f3031b3dd; e28d2af43614eb86f59812e7221735fc221bbc10 up to, but not including, a55677878b93e9ebc31f66d0e2fb93be5e7836a6; e28d2af43614eb86f59812e7221735fc221bbc10 up to, but not including, b7f6c3630eb3f103115ab0d7613588064f665d0d; e28d2af43614eb86f59812e7221735fc221bbc10 up to, but not including, a64ab862e84e3e698cd351a87cdb504c7fc575ca; e28d2af43614eb86f59812e7221735fc221bbc10 up to, but not including, befb7f889594d23e1b475720cf93efd2f77df000; e28d2af43614eb86f59812e7221735fc221bbc10 up to, but not including, 394b6d8bbdf9ddee6d5bcf3e1f3e9f23eecd6484; and 2 more ranges | 7e500849fa558879a1cde43f80c7c048c2437058, 9daddee03de3f231012014dab8ab2b277a116a55, 6470078ab3d8f222115e11c4ec67351f3031b3dd, a55677878b93e9ebc31f66d0e2fb93be5e7836a6, b7f6c3630eb3f103115ab0d7613588064f665d0d, a64ab862e84e3e698cd351a87cdb504c7fc575ca |
| Linux | linux_kernel | 1da177e4c3f4 up to, but not including, 7e500849fa55; 1da177e4c3f4 up to, but not including, 9daddee03de3; 1da177e4c3f4 up to, but not including, 6470078ab3d8; 1da177e4c3f4 up to, but not including, a55677878b93; 1da177e4c3f4 up to, but not including, b7f6c3630eb3; 1da177e4c3f4 up to, but not including, a64ab862e84e; 1da177e4c3f4 up to, but not including, befb7f889594; 1da177e4c3f4 up to, but not including, 394b6d8bbdf9; and 1 more ranges | 7e500849fa55, 9daddee03de3, 6470078ab3d8, a55677878b93, b7f6c3630eb3, a64ab862e84e |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP | V3.1.0 up to, but not including, V3.1.5 | V3.1.5 |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP | V3.1.0 up to, but not including, V3.1.5 | V3.1.5 |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP | V3.1.0 up to, but not including, V3.1.5 | V3.1.5 |
| Debian | Debian Linux | 10.0 | 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: s390/zcrypt: fix reference counting on zcrypt card objects Tests with hot-plugging crytpo cards on KVM guests with debug kernel build revealed an use after free for the load field of the struct zcrypt_card. The reason was an incorrect reference handling of the zcrypt card object which could lead to a free of the zcrypt card object while it was still in use. This is an example of the slab message: kernel: 0x00000000885a7512-0x00000000885a7513 @offset=1298. First byte 0x68 instead of 0x6b kernel: Allocated in zcrypt_card_alloc+0x36/0x70 [zcrypt] age=18046 cpu=3 pid=43 kernel: kmalloc_trace+0x3f2/0x470 kernel: zcrypt_card_alloc+0x36/0x70 [zcrypt] kernel: zcrypt_cex4_card_probe+0x26/0x380 [zcrypt_cex4] kernel: ap_device_probe+0x15c/0x290 kernel: really_probe+0xd2/0x468 kernel: driver_probe_device+0x40/0xf0 kernel: __device_attach_driver+0xc0/0x140 kernel: bus_for_each_drv+0x8c/0xd0 kernel: __device_attach+0x114/0x198 kernel: bus_probe_device+0xb4/0xc8 kernel: device_add+0x4d2/0x6e0 kernel: ap_scan_adapter+0x3d0/0x7c0 kernel: ap_scan_bus+0x5a/0x3b0 kernel: ap_scan_bus_wq_callback+0x40/0x60 kernel: process_one_work+0x26e/0x620 kernel: worker_thread+0x21c/0x440 kernel: Freed in zcrypt_card_put+0x54/0x80 [zcrypt] age=9024 cpu=3 pid=43 kernel: kfree+0x37e/0x418 kernel: zcrypt_card_put+0x54/0x80 [zcrypt] kernel: ap_device_remove+0x4c/0xe0 kernel: device_release_driver_internal+0x1c4/0x270 kernel: bus_remove_device+0x100/0x188 kernel: device_del+0x164/0x3c0 kernel: device_unregister+0x30/0x90 kernel: ap_scan_adapter+0xc8/0x7c0 kernel: ap_scan_bus+0x5a/0x3b0 kernel: ap_scan_bus_wq_callback+0x40/0x60 kernel: process_one_work+0x26e/0x620 kernel: worker_thread+0x21c/0x440 kernel: kthread+0x150/0x168 kernel: __ret_from_fork+0x3c/0x58 kernel: ret_from_fork+0xa/0x30 kernel: Slab 0x00000372022169c0 objects=20 used=18 fp=0x00000000885a7c88 flags=0x3ffff00000000a00(workingset|slab|node=0|zone=1|lastcpupid=0x1ffff) kernel: Object 0x00000000885a74b8 @offset=1208 fp=0x00000000885a7c88 kernel: Redzone 00000000885a74b0: bb bb bb bb bb bb bb bb ........ kernel: Object 00000000885a74b8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk kernel: Object 00000000885a74c8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk kernel: Object 00000000885a74d8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk kernel: Object 00000000885a74e8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk kernel: Object 00000000885a74f8: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk kernel: Object 00000000885a7508: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 68 4b 6b 6b 6b a5 kkkkkkkkkkhKkkk. kernel: Redzone 00000000885a7518: bb bb bb bb bb bb bb bb ........ kernel: Padding 00000000885a756c: 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZ kernel: CPU: 0 PID: 387 Comm: systemd-udevd Not tainted 6.8.0-HF #2 kernel: Hardware name: IBM 3931 A01 704 (KVM/Linux) kernel: Call Trace: kernel: [<00000000ca5ab5b8>] dump_stack_lvl+0x90/0x120 kernel: [<00000000c99d78bc>] check_bytes_and_report+0x114/0x140 kernel: [<00000000c99d53cc>] check_object+0x334/0x3f8 kernel: [<00000000c99d820c>] alloc_debug_processing+0xc4/0x1f8 kernel: [<00000000c99d852e>] get_partial_node.part.0+0x1ee/0x3e0 kernel: [<00000000c99d94ec>] ___slab_alloc+0xaf4/0x13c8 kernel: [<00000000c99d9e38>] __slab_alloc.constprop.0+0x78/0xb8 kernel: [<00000000c99dc8dc>] __kmalloc+0x434/0x590 kernel: [<00000000c9b4c0ce>] ext4_htree_store_dirent+0x4e/0x1c0 kernel: [<00000000c9b908a2>] htree_dirblock_to_tree+0x17a/0x3f0 kernel: ---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/394b6d8bbdf9ddee6d5bcf3e1f3e9f23eecd6484
- git.kernel.org/stable/c/50ed48c80fecbe17218afed4f8bed005c802976c
- git.kernel.org/stable/c/6470078ab3d8f222115e11c4ec67351f3031b3dd
- git.kernel.org/stable/c/7e500849fa558879a1cde43f80c7c048c2437058
- git.kernel.org/stable/c/9daddee03de3f231012014dab8ab2b277a116a55
- git.kernel.org/stable/c/a55677878b93e9ebc31f66d0e2fb93be5e7836a6
- git.kernel.org/stable/c/a64ab862e84e3e698cd351a87cdb504c7fc575ca
- git.kernel.org/stable/c/b7f6c3630eb3f103115ab0d7613588064f665d0d
- git.kernel.org/stable/c/befb7f889594d23e1b475720cf93efd2f77df000
Third-party and government advisories
- lists.debian.org/debian-lts-announce/2024/06/msg00017.htmlMailing List, Third Party Advisory
Other references
Recent Use After Free vulnerabilities
- 9.8 Critical severity
- 8.8 High severity
- 8.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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