CVE-2023-33953 is a high-severity vulnerability found in gRPC, specifically related to HPACK table accounting errors. This vulnerability allows for unexpected disconnects between clients and servers in exceptional cases, leading to denial of service (DoS) attacks. The vulnerability has a CVSS score of 7.5, indicating a high level of risk for organizations that utilize this technology.
The potential for exploitation arises from three main vectors: unbounded memory buffering in the HPACK parser, unbounded CPU consumption in the HPACK parser, and a memory copy bug that results in an O(n^2) parsing loop. The unbounded CPU consumption occurs due to copying that can become excessive based on the input size defined by the client.
The memory buffering issues stem from several factors, including a faulty header size limit check that allows up to a 4 gigabyte string to be buffered before it is rejected. Additionally, HPACK varints can add an infinite number of zeros to integer values, causing the parser to require excessive reads. This vulnerability is compounded by the design of gRPC’s metadata overflow check, which is performed per frame, potentially leading to infinite buffering.
Given these factors, organizations leveraging gRPC must address this vulnerability with urgency. Immediate action is recommended to update to the latest patched versions to mitigate the risks associated with this vulnerability.
Vulnerability Details
The vulnerability is classified as a denial of service (DoS) issue, specifically impacting the availability of the gRPC service. The official description states that the vulnerability allows hpack table accounting errors which could lead to unwanted disconnects between clients and servers. The CVSS score is 7.5, indicating a high severity level due to the potential for significant disruption.
The affected product is gRPC, with the vulnerability being present in versions before 1.53.2, and between 1.54.0 and 1.54.3, as well as 1.55.0 to 1.55.2, and 1.56.0 to 1.56.2. The CVE was published on August 9, 2023.
Technical Analysis
The root cause of this vulnerability lies in the HPACK parser's handling of input data, leading to excessive memory and CPU usage under certain conditions. The attack vector is primarily network-based, with a low attack complexity, requiring no privileges or user interaction. The vulnerability affects availability with a high impact, potentially causing complete service outages.
Risk & Impact Analysis
Risk to organizations includes potential service outages caused by denial of service attacks. Given the widespread use of gRPC in distributed systems, the impact can be substantial, affecting multiple services and leading to a significant blast radius. The urgency for remediation is high, as the vulnerability can be exploited in a network context with low complexity.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The vulnerability affects all gRPC versions prior to 1.53.2, as well as versions 1.54.0 through 1.54.3, 1.55.0 through 1.55.2, and 1.56.0 through 1.56.2.
Mitigation & Remediation
Organizations should prioritize patching immediately. Upgrading to gRPC version 1.53.2 or later is critical to mitigate this vulnerability. In cases where immediate patching is not feasible, organizations should implement network controls to limit exposure and monitor for any unusual patterns in traffic.
Additional guidance may be found in our penetration testing resources to ensure security measures are effectively implemented.
Detection Guidance
To detect potential exploitation of this vulnerability, organizations should monitor logs for indicators of unusual CPU consumption or memory usage patterns. Behavioral anomalies in client-server interactions, especially during high-load scenarios, should also be investigated.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2023-33953 highlights the need for robust validation in parsing logic. This vulnerability represents a trend in software weaknesses that can lead to systemic failures if not addressed. Security teams should learn from this case to strengthen their defenses against similar vulnerabilities in the future.
For further insights into security measures, refer to our penetration testing methodology and best practices.
Additionally, organizations can benefit from our expertise in vulnerability management to effectively address security risks.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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