CVE-2021-23133
Description
A use-after-free flaw was found in the Linux kernel's SCTP socket functionality that triggers a race condition. This flaw allows a local user to escalate their privileges on the system. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability.
Statement
This issue is rated as having a Moderate impact because of the privileges required for running the known reproducer. The required privileges are CAP_BPF and CAP_NET_ADMIN capabilities that are disabled by default in Red Hat Enterprise Linux 7. For Red Hat Enterprise Linux 8, the SCTP protocol itself is disabled by default and cannot be used by a user without enablement by an administrator.
Mitigation
To mitigate this issue, prevent the module sctp from being loaded (and this is so by default for Red Hat Enterprise Linux 8). Please see https://access.redhat.com/solutions/41278 for information on how to blacklist a kernel module to prevent it from loading automatically.
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 | 7 | 6.7 |
| Attack Vector | Local | Local | Local |
| Attack Complexity | High | High | Low |
| Privileges Required | Low | Low | High |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | High | High | High |
| Integrity Impact | High | High | High |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Red Hat CVSS v3 Score Explanation
Suggested that privileges Low required, because at least for the known reproducer the required privileges are CAP_BPF and CAP_NET_ADMIN capabilities that could be used by the user himself (without administrator privileges) by default for some of the Linux systems. For Red Hat these capabilities disabled by default for the regular users. The attack complexity is high, because requires to trigger race condition (so it needs few threads working simultaneously and crash doesn't happen immediately until the kernel with CONFIG_DEBUG_LIST enabled).
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
When a race condition makes it possible to bypass a resource cleanup routine or trigger multiple initialization routines, it may lead to resource exhaustion.
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Instability
When a race condition allows multiple control flows to access a resource simultaneously, it might lead the product(s) into unexpected states, possibly resulting in a crash.
Confidentiality,Integrity
Technical Impact: Read Files or Directories; Read Application Data
When a race condition is combined with predictable resource names and loose permissions, it may be possible for an attacker to overwrite or access confidential data (CWE-59).
Access Control
Technical Impact: Execute Unauthorized Code or Commands; Gain Privileges or Assume Identity; Bypass Protection Mechanism
This can have security implications when the expected synchronization is in security-critical code, such as recording whether a user is authenticated or modifying important state information that should not be influenced by an outsider.
Acknowledgements
Red Hat would like to thank Or Cohen (Palo Alto Networks) for reporting this issue.
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