Linux: Use After Free
CVE-2024-49936 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 3c4423b0c4b98213b3438e15061e1d08220e6982, a7f0073fcd12ed7de185ef2c0af9d0fa1ddef22c, a0465723b8581cad27164c9073fd780904cd22d4 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 0.27% 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 3c4423b0c4b98213b3438e15061e1d08220e6982 or a7f0073fcd12ed7de185ef2c0af9d0fa1ddef22c or a0465723b8581cad27164c9073fd780904cd22d4 or efcff6ce7467f01f0753609f420333f3f2ceceda, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.227 or 5.15.168 or 6.1.113 or 6.6.55, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 40d8abdee806d496a60ee607a6d01b1cd7fabaf0 up to, but not including, 3c4423b0c4b98213b3438e15061e1d08220e6982; 40d8abdee806d496a60ee607a6d01b1cd7fabaf0 up to, but not including, a7f0073fcd12ed7de185ef2c0af9d0fa1ddef22c; 40d8abdee806d496a60ee607a6d01b1cd7fabaf0 up to, but not including, a0465723b8581cad27164c9073fd780904cd22d4; 40d8abdee806d496a60ee607a6d01b1cd7fabaf0 up to, but not including, efcff6ce7467f01f0753609f420333f3f2ceceda; 40d8abdee806d496a60ee607a6d01b1cd7fabaf0 up to, but not including, 143edf098b80669d05245b2f2367dd156a83a2c5; 40d8abdee806d496a60ee607a6d01b1cd7fabaf0 up to, but not including, d408889d4b54f5501e4becc4dbbb9065143fbf4e; 40d8abdee806d496a60ee607a6d01b1cd7fabaf0 up to, but not including, 54d8639af5568fc41c0e274fc3ec9cf86c59fcbb; 40d8abdee806d496a60ee607a6d01b1cd7fabaf0 up to, but not including, 0fa5e94a1811d68fbffa0725efe6d4ca62c03d12; and 1 more ranges | 3c4423b0c4b98213b3438e15061e1d08220e6982, a7f0073fcd12ed7de185ef2c0af9d0fa1ddef22c, a0465723b8581cad27164c9073fd780904cd22d4, efcff6ce7467f01f0753609f420333f3f2ceceda, 143edf098b80669d05245b2f2367dd156a83a2c5, d408889d4b54f5501e4becc4dbbb9065143fbf4e |
| Linux | Linux Kernel | before 5.10.227; 5.11 up to, but not including, 5.15.168; 5.16 up to, but not including, 6.1.113; 6.2 up to, but not including, 6.6.55; 6.7 up to, but not including, 6.10.14; 6.11 up to, but not including, 6.11.3 | 5.10.227, 5.15.168, 6.1.113, 6.6.55, 6.10.14, 6.11.3 |
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 | 8.8 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: net/xen-netback: prevent UAF in xenvif_flush_hash() During the list_for_each_entry_rcu iteration call of xenvif_flush_hash, kfree_rcu does not exist inside the rcu read critical section, so if kfree_rcu is called when the rcu grace period ends during the iteration, UAF occurs when accessing head->next after the entry becomes free. Therefore, to solve this, you need to change it to list_for_each_entry_safe.
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/0fa5e94a1811d68fbffa0725efe6d4ca62c03d12
- git.kernel.org/stable/c/143edf098b80669d05245b2f2367dd156a83a2c5
- git.kernel.org/stable/c/54d8639af5568fc41c0e274fc3ec9cf86c59fcbb
- git.kernel.org/stable/c/a0465723b8581cad27164c9073fd780904cd22d4
- git.kernel.org/stable/c/a7f0073fcd12ed7de185ef2c0af9d0fa1ddef22c
- git.kernel.org/stable/c/d408889d4b54f5501e4becc4dbbb9065143fbf4e
- git.kernel.org/stable/c/efcff6ce7467f01f0753609f420333f3f2ceceda
Other references
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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