CVE-2026-74583
Description
A flaw was found in the Linux kernel's net/sched: cls_route component. A race condition exists in the route4 classifier's fastmap cache, where a reader can re-cache a pointer to a filter that has already been freed by a writer. This can lead to a use-after-free condition, allowing subsequent packet classifications to read from freed memory. The most important consequence is memory corruption, which can result in system instability or a denial of service.
Mitigation
To mitigate this vulnerability, prevent the `cls_route` kernel module from loading. This can be achieved by creating a modprobe configuration file.
1. Create or edit `/etc/modprobe.d/disable-cls_route.conf` and add the following line:
`install cls_route /bin/true`
2. Regenerate the initramfs to ensure the change takes effect on boot:
`dracut -f -v`
3. Reboot the system for the changes to be applied.
Note that disabling this module may impact network traffic classification functionality if it is actively used.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.8 | N/A | 7.8 |
| Attack Vector | Local | N/A | Local |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
If the expired pointer is used in a read operation, an attacker might be able to control data read in by the application.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If the expired pointer references a memory location that is not accessible to the product, or points to a location that is "malformed" (such as NULL) or larger than expected by a read or write operation, then a crash may occur.
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If the expired pointer is used in a function call, or points to unexpected data in a write operation, then code execution may be possible.
Acknowledgements
Red Hat would like to thank Rui Reis and Joshua Foote (XOR at JPMC) for reporting this issue.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
