CVE-2024-1086
Description
A flaw was found in the Netfilter subsystem in the Linux kernel. This issue occurs in the nft_verdict_init() function, allowing positive values as a drop error within the hook verdict, therefore, the nf_hook_slow() function can cause a double-free vulnerability when NF_DROP is issued with a drop error that resembles NF_ACCEPT. The nf_tables component can be exploited to achieve local privilege escalation.
Statement
This flaw is rated as having an Important impact. There is the limitation that it can only be exploited by a local user with access to Netfilter, but can still allow privilege escalation if user namespaces are enabled and Netfilter is being used.
Mitigation
1. This flaw can be mitigated by preventing the affected netfilter (nf_tables) kernel module from being loaded. For instructions on how to blacklist a kernel module, please see https://access.redhat.com/solutions/41278.
2. If the module cannot be disabled, on non-containerized deployments of Red Hat Enterprise Linux, the mitigation is to disable user namespaces:
# echo "user.max_user_namespaces=0" > /etc/sysctl.d/userns.confOn containerized deployments, such as Red Hat OpenShift Container Platform, do not use the second mitigation (disabling user namespaces) as the functionality is needed to be enabled. The first mitigation (blacklisting nf_tables) is still viable for containerized deployments, providing the environment is not using netfilter.
# sysctl -p /etc/sysctl.d/userns.conf
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).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.8 | 7.8 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | High | High | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Red Hat CVSS v3 Score Explanation
The attack vector is use-after-free and later a double-free.
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory
The use of previously freed memory may corrupt valid data, if the memory area in question has been allocated and used properly elsewhere.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If chunk consolidation occurs after the use of previously freed data, the process may crash when invalid data is used as chunk information.
Confidentiality
Technical Impact: Read Memory
Read operations on freed memory can sometimes leak sensitive information instead of causing a crash
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If malicious data is entered before chunk consolidation can take place, it may be possible to take advantage of a write-what-where primitive to execute arbitrary code. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
