Linux: Use After Free
CVE-2024-46786 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 c1fc36d5470335546c45799d94d7bb2cbc09e8b7, e0d724932ad12e3528f4ce97fc0f6078d0cce4bc, 0a11262549ac2ac6fb98c7cd40a67136817e5a52 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 0.23% 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 c1fc36d5470335546c45799d94d7bb2cbc09e8b7 or e0d724932ad12e3528f4ce97fc0f6078d0cce4bc or 0a11262549ac2ac6fb98c7cd40a67136817e5a52 or 72a6e22c604c95ddb3b10b5d3bb85b6ff4dbc34f, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.1.160 or 6.6.51 or 6.10.10, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 12bb21a29c19aae50cfad4e2bb5c943108f34a7d up to, but not including, c1fc36d5470335546c45799d94d7bb2cbc09e8b7; 12bb21a29c19aae50cfad4e2bb5c943108f34a7d up to, but not including, e0d724932ad12e3528f4ce97fc0f6078d0cce4bc; 12bb21a29c19aae50cfad4e2bb5c943108f34a7d up to, but not including, 0a11262549ac2ac6fb98c7cd40a67136817e5a52; 12bb21a29c19aae50cfad4e2bb5c943108f34a7d up to, but not including, 72a6e22c604c95ddb3b10b5d3bb85b6ff4dbc34f; 5.17 | c1fc36d5470335546c45799d94d7bb2cbc09e8b7, e0d724932ad12e3528f4ce97fc0f6078d0cce4bc, 0a11262549ac2ac6fb98c7cd40a67136817e5a52, 72a6e22c604c95ddb3b10b5d3bb85b6ff4dbc34f |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) | V3.1.6 and later; V3.1.7 and later | Not stated |
| Linux | Linux Kernel | 5.17 up to, but not including, 6.1.160; 6.2 up to, but not including, 6.6.51; 6.7 up to, but not including, 6.10.10; 6.11 | 6.1.160, 6.6.51, 6.10.10 |
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.
Official description
In the Linux kernel, the following vulnerability has been resolved: fscache: delete fscache_cookie_lru_timer when fscache exits to avoid UAF The fscache_cookie_lru_timer is initialized when the fscache module is inserted, but is not deleted when the fscache module is removed. If timer_reduce() is called before removing the fscache module, the fscache_cookie_lru_timer will be added to the timer list of the current cpu. Afterwards, a use-after-free will be triggered in the softIRQ after removing the fscache module, as follows: ================================================================== BUG: unable to handle page fault for address: fffffbfff803c9e9 PF: supervisor read access in kernel mode PF: error_code(0x0000) - not-present page PGD 21ffea067 P4D 21ffea067 PUD 21ffe6067 PMD 110a7c067 PTE 0 Oops: Oops: 0000 [#1] PREEMPT SMP KASAN PTI CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Tainted: G W 6.11.0-rc3 #855 Tainted: [W]=WARN RIP: 0010:__run_timer_base.part.0+0x254/0x8a0 Call Trace: <IRQ> tmigr_handle_remote_up+0x627/0x810 __walk_groups.isra.0+0x47/0x140 tmigr_handle_remote+0x1fa/0x2f0 handle_softirqs+0x180/0x590 irq_exit_rcu+0x84/0xb0 sysvec_apic_timer_interrupt+0x6e/0x90 </IRQ> <TASK> asm_sysvec_apic_timer_interrupt+0x1a/0x20 RIP: 0010:default_idle+0xf/0x20 default_idle_call+0x38/0x60 do_idle+0x2b5/0x300 cpu_startup_entry+0x54/0x60 start_secondary+0x20d/0x280 common_startup_64+0x13e/0x148 </TASK> Modules linked in: [last unloaded: netfs] ================================================================== Therefore delete fscache_cookie_lru_timer when removing the fscahe module.
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
Recent Use After Free vulnerabilities
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