Linux: Use After Free
CVE-2022-49779 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 7b0007b28dd970176f2e297c06ae63eea2447127, 7d606ae1abcc3eab5408e42444d789dc7def51b8, c49cc2c059b503e962c2f13a806c105f9b757df4 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 7b0007b28dd970176f2e297c06ae63eea2447127 or 7d606ae1abcc3eab5408e42444d789dc7def51b8 or c49cc2c059b503e962c2f13a806c105f9b757df4 or 55788ebbe8b365b4375bd56b4ba7db79d393a370, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.4.225 or 5.10.156 or 5.15.80 or 6.0.10, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 0bc11ed5ab60c135aa764a62c02cd5ea68289de4 up to, but not including, 7b0007b28dd970176f2e297c06ae63eea2447127; 0bc11ed5ab60c135aa764a62c02cd5ea68289de4 up to, but not including, 7d606ae1abcc3eab5408e42444d789dc7def51b8; 0bc11ed5ab60c135aa764a62c02cd5ea68289de4 up to, but not including, c49cc2c059b503e962c2f13a806c105f9b757df4; 0bc11ed5ab60c135aa764a62c02cd5ea68289de4 up to, but not including, 55788ebbe8b365b4375bd56b4ba7db79d393a370; 0bc11ed5ab60c135aa764a62c02cd5ea68289de4 up to, but not including, 5dd7caf0bdc5d0bae7cf9776b4d739fb09bd5ebb; 5.4 | 7b0007b28dd970176f2e297c06ae63eea2447127, 7d606ae1abcc3eab5408e42444d789dc7def51b8, c49cc2c059b503e962c2f13a806c105f9b757df4, 55788ebbe8b365b4375bd56b4ba7db79d393a370, 5dd7caf0bdc5d0bae7cf9776b4d739fb09bd5ebb |
| Linux | Linux Kernel | 5.4 up to, but not including, 5.4.225; 5.5 up to, but not including, 5.10.156; 5.11 up to, but not including, 5.15.80; 5.16 up to, but not including, 6.0.10; 6.1 | 5.4.225, 5.10.156, 5.15.80, 6.0.10 |
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: kprobes: Skip clearing aggrprobe's post_handler in kprobe-on-ftrace case In __unregister_kprobe_top(), if the currently unregistered probe has post_handler but other child probes of the aggrprobe do not have post_handler, the post_handler of the aggrprobe is cleared. If this is a ftrace-based probe, there is a problem. In later calls to disarm_kprobe(), we will use kprobe_ftrace_ops because post_handler is NULL. But we're armed with kprobe_ipmodify_ops. This triggers a WARN in __disarm_kprobe_ftrace() and may even cause use-after-free: Failed to disarm kprobe-ftrace at kernel_clone+0x0/0x3c0 (error -2) WARNING: CPU: 5 PID: 137 at kernel/kprobes.c:1135 __disarm_kprobe_ftrace.isra.21+0xcf/0xe0 Modules linked in: testKprobe_007(-) CPU: 5 PID: 137 Comm: rmmod Not tainted 6.1.0-rc4-dirty #18 [...] Call Trace: <TASK> __disable_kprobe+0xcd/0xe0 __unregister_kprobe_top+0x12/0x150 ? mutex_lock+0xe/0x30 unregister_kprobes.part.23+0x31/0xa0 unregister_kprobe+0x32/0x40 __x64_sys_delete_module+0x15e/0x260 ? do_user_addr_fault+0x2cd/0x6b0 do_syscall_64+0x3a/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd [...] For the kprobe-on-ftrace case, we keep the post_handler setting to identify this aggrprobe armed with kprobe_ipmodify_ops. This way we can disarm it correctly.
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
- git.kernel.org/stable/c/55788ebbe8b365b4375bd56b4ba7db79d393a370
- git.kernel.org/stable/c/5dd7caf0bdc5d0bae7cf9776b4d739fb09bd5ebb
- git.kernel.org/stable/c/7b0007b28dd970176f2e297c06ae63eea2447127
- git.kernel.org/stable/c/7d606ae1abcc3eab5408e42444d789dc7def51b8
- git.kernel.org/stable/c/c49cc2c059b503e962c2f13a806c105f9b757df4
Recent Use After Free vulnerabilities
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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