CVE-2026-27171 is a low-severity vulnerability identified in zlib versions prior to 1.3.2. This vulnerability allows CPU consumption via the functions crc32_combine64 and crc32_combine_gen64, due to the x2nmodp function performing right shifts within a loop without a termination condition. As a result, the affected versions may experience performance degradation under certain conditions.
The vulnerability has received a CVSS base score of 2.9, indicating a low severity level. The attack vector is local, and the complexity is high, meaning that exploiting this vulnerability requires an attacker to have a certain level of access and skill. The potential impact on availability is rated as low, while confidentiality and integrity impacts are assessed as none.
Risk to organizations includes potential performance degradation in systems using vulnerable versions of zlib, especially in resource-constrained environments. It is crucial for organizations to identify any use of the affected library and assess their operational impact. Organizations should prioritize patching immediately.
As of now, there are no known public exploits or proofs of concept available. This suggests that while the vulnerability is present, active exploitation in the wild has not been reported, reducing immediate urgency but not eliminating the need for remediation.
Vulnerability Details
The official description states that zlib before 1.3.2 allows CPU consumption via crc32_combine64 and crc32_combine_gen64 because the x2nmodp function can perform right shifts without a loop termination condition. This leads to excessive CPU usage, which can affect the overall performance of applications relying on this library.
The CVSS score assigned to this vulnerability is 2.9, which classifies it as low severity. This assessment is based on factors such as the attack vector being local, high attack complexity, and no required privileges or user interaction. The availability impact is rated as low, while confidentiality and integrity impacts are nonexistent.
The vulnerability affects versions of zlib from 1.2.12 up to but not including 1.3.2, as specified in the Common Platform Enumeration (CPE) entry.
Technical Analysis
The root cause of CVE-2026-27171 lies in a loop within the x2nmodp function that lacks a termination condition. This allows for infinite iterations, leading to sustained CPU consumption. The attack vector is local, meaning an attacker must have access to the system running the affected version of zlib.
The complexity of exploiting this vulnerability is high, as it requires an attacker to have knowledge of the library's internal workings and the ability to manipulate its execution. No user interaction is required for exploitation, and the necessary privileges are none.
In terms of impact, the vulnerability does not affect confidentiality or integrity, but it can degrade the availability of systems using vulnerable versions of zlib.
Risk & Impact Analysis
Organizations using vulnerable versions of zlib face potential CPU exhaustion, which can lead to degraded performance. The risk is particularly pertinent in scenarios where the library is used in high-performance applications or systems with limited resources.
This vulnerability could have a broader blast radius, especially in shared environments where multiple applications utilize zlib. Any performance degradation could impact not only the affected application but also others that share resources.
Given the current CVSS score of 2.9 and the lack of known exploitation, organizations may approach remediation with moderate urgency. However, they should still schedule remediation as part of their regular maintenance processes.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
This vulnerability affects all versions of zlib prior to 1.3.2, specifically those starting from 1.2.12 up to but not including 1.3.2. Organizations should ensure that they are using the latest version to mitigate this vulnerability.
Mitigation & Remediation
Organizations should upgrade to zlib version 1.3.2 or later to mitigate this vulnerability. If an immediate upgrade is not feasible, consider implementing workarounds such as limiting the use of the affected functions in critical applications.
For ongoing protection, organizations may also benefit from conducting regular security assessments. Engaging in penetration testing can help identify similar vulnerabilities in the future.
Detection Guidance
Monitoring for abnormal CPU usage patterns in applications utilizing zlib can help detect potential exploitation of this vulnerability. Additionally, keep an eye on logs for any unusual function calls related to crc32_combine64 and crc32_combine_gen64.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2026-27171 highlights the necessity for organizations to maintain up-to-date libraries and frameworks, as outdated versions can harbor vulnerabilities that may be exploited over time. This incident serves as a reminder of the importance of proactive vulnerability management.
Security teams should recognize patterns in library dependencies and prioritize regular audits. For further information on managing vulnerabilities, organizations can explore the resources available in the vulnerability management program and assess their approach to security testing through penetration testing methodology implementation.
In conclusion, CVE-2026-27171 serves as a critical reminder for organizations to ensure that they utilize the latest versions of libraries like zlib, thereby mitigating risks associated with known vulnerabilities.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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