CVE-2025-66199
Description
A flaw was found in OpenSSL. A remote attacker can exploit this vulnerability by sending a specially crafted CompressedCertificate message during the TLS 1.3 handshake. This can cause excessive per-connection memory allocations, leading to resource exhaustion and a Denial of Service (DoS) for affected clients and servers. This issue occurs when TLS 1.3 certificate compression is enabled and negotiated.
Statement
This vulnerability is rated Low for Red Hat products. The flaw in OpenSSL 3.3, 3.4, 3.5, and 3.6 allows an attacker to cause excessive memory allocation during TLS 1.3 handshake with certificate compression, potentially leading to a Denial of Service. This affects both clients and servers in mutual TLS scenarios where certificate compression is negotiated. Servers not requesting client certificates are not vulnerable to client-initiated attacks.
Mitigation
To mitigate this issue, disable the reception of compressed certificates by setting the SSL_OP_NO_RX_CERTIFICATE_COMPRESSION option in OpenSSL configurations. This will prevent the vulnerable code path from being exercised.
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 | N/A | 5.9 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
When allocating resources without limits, an attacker could prevent other systems, applications, or processes from accessing the same type of resource. It can be easy for an attacker to consume many resources by rapidly making many requests or causing larger resources to be used than is needed.
Frequently Asked Questions
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