Linux: Use After Free
CVE-2022-49921 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 795afe0b9bb6c915f0299a8e309936519be01619, a238cdcf2bdc72207c74375fc8be13ee549ca9db, e877f8fa49fbccc63cb2df2e9179bddc695b825a 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 0.19% 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 795afe0b9bb6c915f0299a8e309936519be01619 or a238cdcf2bdc72207c74375fc8be13ee549ca9db or e877f8fa49fbccc63cb2df2e9179bddc695b825a or 52e0429471976785c155bfbf51d80990c6cd46e2, whichever matches your release line, or a later version.
- Update Linux Kernel to 4.5 or 4.9.333 or 4.14.299 or 4.19.265, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | d7f4f332f082c4d4ba53582f902ed6b44fd6f45e up to, but not including, 795afe0b9bb6c915f0299a8e309936519be01619; d7f4f332f082c4d4ba53582f902ed6b44fd6f45e up to, but not including, a238cdcf2bdc72207c74375fc8be13ee549ca9db; d7f4f332f082c4d4ba53582f902ed6b44fd6f45e up to, but not including, e877f8fa49fbccc63cb2df2e9179bddc695b825a; d7f4f332f082c4d4ba53582f902ed6b44fd6f45e up to, but not including, 52e0429471976785c155bfbf51d80990c6cd46e2; d7f4f332f082c4d4ba53582f902ed6b44fd6f45e up to, but not including, 5960b9081baca85cc7dcb14aec1de85999ea9d36; d7f4f332f082c4d4ba53582f902ed6b44fd6f45e up to, but not including, fc4b50adb400ee5ec527a04073174e8e73a139fa; d7f4f332f082c4d4ba53582f902ed6b44fd6f45e up to, but not including, 170e5317042c302777ed6d59fdb84af9b0219d4e; d7f4f332f082c4d4ba53582f902ed6b44fd6f45e up to, but not including, 8bdc2acd420c6f3dd1f1c78750ec989f02a1e2b9; and 3 more ranges | 795afe0b9bb6c915f0299a8e309936519be01619, a238cdcf2bdc72207c74375fc8be13ee549ca9db, e877f8fa49fbccc63cb2df2e9179bddc695b825a, 52e0429471976785c155bfbf51d80990c6cd46e2, 5960b9081baca85cc7dcb14aec1de85999ea9d36, fc4b50adb400ee5ec527a04073174e8e73a139fa |
| Linux | Linux Kernel | 4.4.163 up to, but not including, 4.5; 4.7 up to, but not including, 4.9.333; 4.10 up to, but not including, 4.14.299; 4.15 up to, but not including, 4.19.265; 4.20 up to, but not including, 5.4.224; 5.5 up to, but not including, 5.10.154; 5.11 up to, but not including, 5.15.78; 5.16 up to, but not including, 6.0.8; and 1 more ranges | 4.5, 4.9.333, 4.14.299, 4.19.265, 5.4.224, 5.10.154 |
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 | 7.8 | High | NVD |
| CVSS 3.1 | 7.8 | High | CISA (ADP) |
Official description
In the Linux kernel, the following vulnerability has been resolved: net: sched: Fix use after free in red_enqueue() We can't use "skb" again after passing it to qdisc_enqueue(). This is basically identical to commit 2f09707d0c97 ("sch_sfb: Also store skb len before calling child enqueue").
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/170e5317042c302777ed6d59fdb84af9b0219d4e
- git.kernel.org/stable/c/52e0429471976785c155bfbf51d80990c6cd46e2
- git.kernel.org/stable/c/5960b9081baca85cc7dcb14aec1de85999ea9d36
- git.kernel.org/stable/c/795afe0b9bb6c915f0299a8e309936519be01619
- git.kernel.org/stable/c/8bdc2acd420c6f3dd1f1c78750ec989f02a1e2b9
- git.kernel.org/stable/c/a238cdcf2bdc72207c74375fc8be13ee549ca9db
- git.kernel.org/stable/c/e877f8fa49fbccc63cb2df2e9179bddc695b825a
- git.kernel.org/stable/c/fc4b50adb400ee5ec527a04073174e8e73a139fa
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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