The vulnerability identified as CVE-2026-31970 affects htslib, a library used for reading and writing bioinformatics file formats. It allows for a heap buffer overflow due to an integer overflow in the GZI loading function, `bgzf_index_load_hfile()`. This issue can lead to unexpected program crashes or data corruption, potentially allowing for arbitrary code execution. The severity of this vulnerability is rated high, with a CVSS score of 7.1. Organizations using affected versions should consider the risk to their systems.
The vulnerability has been confirmed in versions up to 1.23.1, with specific fixes provided in versions 1.23.1, 1.22.2, and 1.21.1. Due to the nature of this flaw, it is critical that organizations take immediate action to patch their systems. The risk to organizations includes the potential for unauthorized access or data manipulation through exploitation of this vulnerability.
Given the urgency, organizations should prioritize patching immediately. Users are advised to discard any `.gzi` index files from untrusted sources and use the `bgzip -r` option to recreate them. The potential impact of this vulnerability necessitates swift action to protect sensitive data and maintain the integrity of systems reliant on htslib.
As of the latest information, there is no public evidence of active exploitation of this vulnerability. However, the technical details indicate that it could be leveraged by attackers to gain access to critical systems, further emphasizing the importance of remediation.
Vulnerability Details
HTSlib is a library for reading and writing bioinformatics file formats. GZI files are used to index block-compressed GZIP [BGZF] files. In the GZI loading function, `bgzf_index_load_hfile()`, it was possible to trigger an integer overflow, leading to an under- or zero-sized buffer being allocated to store the index. Sixteen zero bytes would then be written to this buffer, and, depending on the result of the overflow, the rest of the file may also be loaded into the buffer as well. If the function did attempt to load the data, it would eventually fail due to not reading the expected number of records, and then try to free the overflowed heap buffer. Exploiting this bug causes a heap buffer overflow. If a user opens a file crafted to exploit this issue, it could lead to the program crashing, or overwriting of data and heap structures in ways not expected by the program. It may be possible to use this to obtain arbitrary code execution.
The CVSS score for this vulnerability is 7.1, categorizing it as high severity. The vulnerability is classified under multiple CWE identifiers, including CWE-122 (Heap-based Buffer Overflow), CWE-131 (Incorrect Calculation), CWE-190 (Integer Overflow or Wraparound), CWE-787 (Out-of-bounds Write), and CWE-1284 (Buffer Overflow in Fixed-size Buffer).
Technical Analysis
The root cause of the vulnerability lies in the integer overflow that occurs during the loading of GZI files. The attack vector is network-based, and the attack complexity is low, allowing for the potential exploitation of this vulnerability without requiring advanced skills. No privileges are required for exploitation, as the user interaction is passive, meaning that merely opening a malicious file could trigger the exploit.
The impacts of this vulnerability are significant, with a high integrity impact and a low availability impact. Confidentiality is not affected, but the integrity of the data and the availability of the application could be compromised. Monitoring for abnormal behavior when processing GZIP files is recommended.
Risk & Impact Analysis
The deployment of this vulnerability in real-world scenarios poses a substantial risk to organizations using htslib. The potential for arbitrary code execution makes it a critical issue that should not be underestimated. Organizations must assess their exposure to this vulnerability and the potential blast radius in terms of data integrity and system availability.
Given the CVSS score, organizations should address this vulnerability in priority patch cycles. The potential for exploitation is significant enough to warrant immediate attention. Organizations must ensure they have appropriate defenses in place, including monitoring and incident response capabilities, to mitigate the risks associated with this vulnerability.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The affected versions of htslib include all versions prior to vendor patch, specifically those versions that include fixes for this issue: 1.23.1, 1.22.2, and 1.21.1. Organizations should ensure they are running an updated version to mitigate the risks associated with this vulnerability.
Mitigation & Remediation
To mitigate this vulnerability, organizations should prioritize patching and update to the latest version of htslib. If a patch is not immediately available, it is recommended to discard any `.gzi` index files from untrusted sources and use the `bgzip -r` option to recreate them. Additionally, organizations should implement configuration hardening and network controls to prevent unauthorized access to their systems.
For more comprehensive security practices, organizations can engage in penetration testing to evaluate the effectiveness of their defenses against potential exploits.
Detection Guidance
Organizations should monitor logs for indicators of exploitation, particularly attempts to load `.gzi` files. Behavioral anomalies during file processing operations may indicate potential exploitation attempts. Network signatures associated with the transfer of malicious GZI files should also be tracked, and system changes related to the htslib environment should be closely observed.
AppSecure Threat Intelligence Insight
In conclusion, CVE-2026-31970 represents a significant vulnerability that could have serious repercussions if left unaddressed. Security teams should be aware of the implications of this vulnerability and implement strategies to mitigate potential risks. Regular updates and audits of library dependencies can help reduce the attack surface.
To stay informed on similar vulnerabilities and improve overall security posture, organizations are encouraged to review current best practices for penetration testing methodology and consider comprehensive security assessments.
For organizations using htslib, addressing this vulnerability should be a top priority to ensure the security of their bioinformatics applications.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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