Raw vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XSummary
CVE-2026-31962 is a high-severity Heap-based Buffer Overflow (CWE-122) vulnerability in Htslib Htslib. Its CVSS base score is 8.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 29th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-31962 is a heap buffer overflow vulnerability in HTSlib, a C library for reading and writing bioinformatics file formats such as CRAM, which stores compressed DNA sequence alignment data. The issue arises in the `cram_decode_seq()` function, which fails to properly handle CRAM records that omit DNA sequence and quality values to save space. In affected cases, this leads to reading a single byte beyond the end of a heap allocation followed by writing an attacker-controlled byte to the same location, enabling heap structure corruption.
The vulnerability can be exploited by any remote attacker with no privileges required (PR:N) who tricks a user into opening a specially crafted CRAM file (UI:R), as indicated by the CVSS 3.1 score of 8.8 (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H). Successful exploitation may cause the affected program to crash, overwrite arbitrary data or heap structures, and potentially achieve arbitrary code execution.
Patches are available in HTSlib versions 1.23.1, 1.22.2, and 1.21.1, as detailed in the project's GitHub security advisory (GHSA-xxmp-v7h3-gpwp) and the fixing commit (d799b54c6401879187bba4741be83ff590ac73e3). There is no workaround for this issue. The vulnerability is associated with CWEs-122 (Heap-based Buffer Overflow), CWE-125 (Out-of-bounds Read), CWE-129 (Improper Validation of Array Index), and CWE-787 (Out-of-bounds Write).
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-12923
Vulnerability Data
HTSlib is a library for reading and writing bioinformatics file formats. CRAM is a compressed format which stores DNA sequence alignment data. While most alignment records store DNA sequence and quality values, the format also allows them to omit this…
more
data in certain cases to save space. Due to some quirks of the CRAM format, it is necessary to handle these records carefully as they will actually store data that needs to be consumed and then discarded. Unfortunately the `cram_decode_seq()` did not handle this correctly in some cases. Where this happened it could result in reading a single byte from beyond the end of a heap allocation, followed by writing a single attacker-controlled byte to the same location. 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. Versions 1.23.1, 1.22.2 and 1.21.1 include fixes for this issue. There is no workaround for this issue.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
—
—
—
V1.4.1
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation (including fuzzing and memory-error detectors) can discover heap overflows after they have been coded.
Input validation enforces bounds checking on data written to heap buffers, directly stopping the overflow condition from being introduced.
Requiring documented secure-development standards and tools can mandate bounds-checked coding practices that avoid the weakness.
Security engineering principles require use of memory-safe constructs and bounds-checked allocation routines that avoid introducing heap overflows.
Process isolation confines the effects of an out-of-bounds read to the compromised process.
Memory-protection mechanisms limit the ability of a heap overflow to execute attacker-controlled code or corrupt adjacent structures.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure-development practices directly require bounds checking and safe memory handling that prevent heap overflows.
Vulnerability scanning and recording can discover heap-overflow flaws but does not prevent their introduction in code.
Timely patching removes known heap-overflow instances after they exist.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development and acceptance can detect heap overflows before release.
Logging can record evidence of an out-of-bounds read but does not prevent the weakness itself.
Secure development lifecycle mandates practices that reduce the likelihood of introducing heap overflows.
Application security requirements can specify bounds-checking and safe memory APIs that mitigate heap overflows.
Secure architecture and engineering principles include memory-safety and input-validation controls that address heap overflows.
Secure coding standards directly prescribe techniques (safe functions, bounds checks) that prevent heap-based buffer overflows.