Linux: Use After Free
CVE-2024-40920 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 caaa2129784a04dcade0ea92c12e6ff90bbd23d8, 7caefa2771722e65496d85b62e1dc4442b7d1345, 406bfc04b01ee47e4c626f77ecc7d9f85135b166 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 0.41% 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 caaa2129784a04dcade0ea92c12e6ff90bbd23d8 or 7caefa2771722e65496d85b62e1dc4442b7d1345 or 406bfc04b01ee47e4c626f77ecc7d9f85135b166 or 546ceb1dfdac866648ec959cbc71d9525bd73462, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.1.95 or 6.6.35 or 6.9 or 6.9.6, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 8ca9a750fc711911ef616ceb627d07357b04545e up to, but not including, caaa2129784a04dcade0ea92c12e6ff90bbd23d8; 4488617e5e995a09abe4d81add5fb165674edb59 up to, but not including, 7caefa2771722e65496d85b62e1dc4442b7d1345; e43dd2b1ec746e105b7db5f9ad6ef14685a615a4 up to, but not including, 406bfc04b01ee47e4c626f77ecc7d9f85135b166; 3a7c1661ae1383364cd6092d851f5e5da64d476b up to, but not including, 546ceb1dfdac866648ec959cbc71d9525bd73462; a2b01e65d9ba8af2bb086d3b7288ca53a07249ac; 6.8.12 up to, but not including, 6.9; 6.1.93 up to, but not including, 6.1.95; 6.6.33 up to, but not including, 6.6.35; and 1 more ranges | caaa2129784a04dcade0ea92c12e6ff90bbd23d8, 7caefa2771722e65496d85b62e1dc4442b7d1345, 406bfc04b01ee47e4c626f77ecc7d9f85135b166, 546ceb1dfdac866648ec959cbc71d9525bd73462, 6.9, 6.1.95 |
| Linux | Linux Kernel | 6.1.93 up to, but not including, 6.1.95; 6.6.33 up to, but not including, 6.6.35; 6.8.12 up to, but not including, 6.9; 6.9.3 up to, but not including, 6.9.6; 6.10 | 6.1.95, 6.6.35, 6.9, 6.9.6 |
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 | 7.1 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: net: bridge: mst: fix suspicious rcu usage in br_mst_set_state I converted br_mst_set_state to RCU to avoid a vlan use-after-free but forgot to change the vlan group dereference helper. Switch to vlan group RCU deref helper to fix the suspicious rcu usage warning.
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
- 7.8 High severity
- 7.8 High severity
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- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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