Linux: Use After Free
CVE-2022-49956 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 7dce6b0ee7d78667d6c831ced957a08769973063, 376e15487fec837301d888068a3fcc82efb6171a, 9fd6170c5e2d0ccd027abe26f6f5ffc528e1bb27 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 0.26% 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 7dce6b0ee7d78667d6c831ced957a08769973063 or 376e15487fec837301d888068a3fcc82efb6171a or 9fd6170c5e2d0ccd027abe26f6f5ffc528e1bb27 or d0aac7146e96bf39e79c65087d21dfa02ef8db38, whichever matches your release line, or a later version.
- Update Linux Kernel to 4.9.328 or 4.14.293 or 4.19.258 or 5.4.213, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 2865d42c78a9121caad52cb02d1fbb7f5cdbc4ef up to, but not including, 7dce6b0ee7d78667d6c831ced957a08769973063; 2865d42c78a9121caad52cb02d1fbb7f5cdbc4ef up to, but not including, 376e15487fec837301d888068a3fcc82efb6171a; 2865d42c78a9121caad52cb02d1fbb7f5cdbc4ef up to, but not including, 9fd6170c5e2d0ccd027abe26f6f5ffc528e1bb27; 2865d42c78a9121caad52cb02d1fbb7f5cdbc4ef up to, but not including, d0aac7146e96bf39e79c65087d21dfa02ef8db38; 2865d42c78a9121caad52cb02d1fbb7f5cdbc4ef up to, but not including, 19e3f69d19801940abc2ac37c169882769ed9770; 2865d42c78a9121caad52cb02d1fbb7f5cdbc4ef up to, but not including, dc02aaf950015850e7589696521c7fca767cea77; 2865d42c78a9121caad52cb02d1fbb7f5cdbc4ef up to, but not including, b1727def850904e4b8ba384043775672841663a1; 2865d42c78a9121caad52cb02d1fbb7f5cdbc4ef up to, but not including, e230a4455ac3e9b112f0367d1b8e255e141afae0; and 1 more ranges | 7dce6b0ee7d78667d6c831ced957a08769973063, 376e15487fec837301d888068a3fcc82efb6171a, 9fd6170c5e2d0ccd027abe26f6f5ffc528e1bb27, d0aac7146e96bf39e79c65087d21dfa02ef8db38, 19e3f69d19801940abc2ac37c169882769ed9770, dc02aaf950015850e7589696521c7fca767cea77 |
| Linux | Linux Kernel | 2.6.37 up to, but not including, 4.9.328; 4.10 up to, but not including, 4.14.293; 4.15 up to, but not including, 4.19.258; 4.20 up to, but not including, 5.4.213; 5.5 up to, but not including, 5.10.142; 5.11 up to, but not including, 5.15.66; 5.16 up to, but not including, 5.19.8; 6.0 | 4.9.328, 4.14.293, 4.19.258, 5.4.213, 5.10.142, 5.15.66 |
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 | 7.0 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: staging: rtl8712: fix use after free bugs _Read/Write_MACREG callbacks are NULL so the read/write_macreg_hdl() functions don't do anything except free the "pcmd" pointer. It results in a use after free. Delete them.
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.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/19e3f69d19801940abc2ac37c169882769ed9770
- git.kernel.org/stable/c/376e15487fec837301d888068a3fcc82efb6171a
- git.kernel.org/stable/c/7dce6b0ee7d78667d6c831ced957a08769973063
- git.kernel.org/stable/c/9fd6170c5e2d0ccd027abe26f6f5ffc528e1bb27
- git.kernel.org/stable/c/b1727def850904e4b8ba384043775672841663a1
- git.kernel.org/stable/c/d0aac7146e96bf39e79c65087d21dfa02ef8db38
- git.kernel.org/stable/c/dc02aaf950015850e7589696521c7fca767cea77
- git.kernel.org/stable/c/e230a4455ac3e9b112f0367d1b8e255e141afae0
Recent Use After Free vulnerabilities
- 8.8 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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