Linux: Use After Free
CVE-2022-50241 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 bbacfcde5fff25ac22597e8373a065c647da6738, 83b94969751a691347606dbe6b1865efcfa5a643, 6ea71246b7a02af675d733e72d14bd0d591d5f4a 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 0.37% 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 bbacfcde5fff25ac22597e8373a065c647da6738 or 83b94969751a691347606dbe6b1865efcfa5a643 or 6ea71246b7a02af675d733e72d14bd0d591d5f4a or 35aa0fb8c3033a3d78603356e96fc18c5b9cceb2, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.10.150 or 5.15.75 or 5.19.17 or 6.0.3, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 624322f1adc58acd0b69f77a6ddc764207e97241 up to, but not including, bbacfcde5fff25ac22597e8373a065c647da6738; 624322f1adc58acd0b69f77a6ddc764207e97241 up to, but not including, 83b94969751a691347606dbe6b1865efcfa5a643; 624322f1adc58acd0b69f77a6ddc764207e97241 up to, but not including, 6ea71246b7a02af675d733e72d14bd0d591d5f4a; 624322f1adc58acd0b69f77a6ddc764207e97241 up to, but not including, 35aa0fb8c3033a3d78603356e96fc18c5b9cceb2; 624322f1adc58acd0b69f77a6ddc764207e97241 up to, but not including, 019805fea91599b22dfa62ffb29c022f35abeb06; 5.6 | bbacfcde5fff25ac22597e8373a065c647da6738, 83b94969751a691347606dbe6b1865efcfa5a643, 6ea71246b7a02af675d733e72d14bd0d591d5f4a, 35aa0fb8c3033a3d78603356e96fc18c5b9cceb2, 019805fea91599b22dfa62ffb29c022f35abeb06 |
| Linux | Linux Kernel | before 5.10.150; 5.11 up to, but not including, 5.15.75; 5.16 up to, but not including, 5.19.17; 6.0 up to, but not including, 6.0.3 | 5.10.150, 5.15.75, 5.19.17, 6.0.3 |
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: NFSD: fix use-after-free on source server when doing inter-server copy Use-after-free occurred when the laundromat tried to free expired cpntf_state entry on the s2s_cp_stateids list after inter-server copy completed. The sc_cp_list that the expired copy state was inserted on was already freed. When COPY completes, the Linux client normally sends LOCKU(lock_state x), FREE_STATEID(lock_state x) and CLOSE(open_state y) to the source server. The nfs4_put_stid call from nfsd4_free_stateid cleans up the copy state from the s2s_cp_stateids list before freeing the lock state's stid. However, sometimes the CLOSE was sent before the FREE_STATEID request. When this happens, the nfsd4_close_open_stateid call from nfsd4_close frees all lock states on its st_locks list without cleaning up the copy state on the sc_cp_list list. When the time the FREE_STATEID arrives the server returns BAD_STATEID since the lock state was freed. This causes the use-after-free error to occur when the laundromat tries to free the expired cpntf_state. This patch adds a call to nfs4_free_cpntf_statelist in nfsd4_close_open_stateid to clean up the copy state before calling free_ol_stateid_reaplist to free the lock state's stid on the reaplist.
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: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/019805fea91599b22dfa62ffb29c022f35abeb06
- git.kernel.org/stable/c/35aa0fb8c3033a3d78603356e96fc18c5b9cceb2
- git.kernel.org/stable/c/6ea71246b7a02af675d733e72d14bd0d591d5f4a
- git.kernel.org/stable/c/83b94969751a691347606dbe6b1865efcfa5a643
- git.kernel.org/stable/c/bbacfcde5fff25ac22597e8373a065c647da6738
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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