CVE-2023-0464
Description
A security vulnerability has been identified in all supported OpenSSL versions related to verifying X.509 certificate chains that include policy constraints. This flaw allows attackers to exploit this vulnerability by creating a malicious certificate chain that triggers exponential use of computational resources, leading to a denial of service (DoS) attack on affected systems. Policy processing is disabled by default but can be enabled by passing the -policy' argument to the command line utilities or calling the X509_VERIFY_PARAM_set1_policies()' function.
Statement
This vulnerability is classified as low severity because policy processing in OpenSSL is disabled by default, meaning that most deployments are unaffected unless explicitly configured to enable policy checks. Additionally, while the flaw can cause exponential computational resource consumption, it does not allow for remote code execution, memory corruption, or data exfiltration—limiting its impact to a denial-of-service (DoS) condition. Exploiting this issue also requires an attacker to supply a specifically crafted X.509 certificate chain, which is only feasible in scenarios where certificate validation of untrusted chains is performed, further reducing the practical risk.
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 | 5.9 | 7.5 | 7.5 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | High | Low | Low |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | None | None | None |
| Integrity Impact | None | None | None |
| Availability Impact | High | High | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Red Hat CVSS v3 Score Explanation
A successful attack depends on conditions beyond the attacker's control, so Attack Complexity marked as High.
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
If an attacker can trigger the allocation of the limited resources, but the number or size of the resources is not controlled, then the most common result is denial of service. This would prevent valid users from accessing the product, and it could potentially have an impact on the surrounding environment, i.e., the product may slow down, crash due to unhandled errors, or lock out legitimate users. For example, a memory exhaustion attack against an application could slow down the application as well as its host operating system.
Access Control,Other
Technical Impact: Bypass Protection Mechanism; Other
In some cases it may be possible to force the product to "fail open" in the event of resource exhaustion. The state of the product -- and possibly the security functionality - may then be compromised.
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