Out-of-bounds Read in Htslib
CVE-2026-31965
HTSlib is a library for reading and writing bioinformatics file formats. CRAM is a compressed format which stores DNA sequence alignment data. In the `cram_decode_slice()` function called while reading CRAM records, validation of the reference id field occurred too late, allowing two out of bounds reads to occur before the invalid data was detected. The bug does allow two values to be leaked to the caller, however as the function reports an error it may be difficult to exploit them. It is also possible that the program will crash due to trying to access invalid memory. Versions 1.23.1, 1.22.2 and 1.21.1 include fixes for this issue. There is no workaround for this issue.
Vulnerability class: Buffer Overflow
EPSS: 0.004 (30.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 8.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H.
Affected products
- Htslib — versions 1.23
- Samtools Htslib — versions < 1.21.1, >= 1.22, < 1.22.2, = 1.23
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Patch, Vendor Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC)
Frequently asked questions
- What is CVE-2026-31965?
- CVE-2026-31965 is a high-severity vulnerability in Htslib, classified under Out-of-bounds Read. CVSS score: 8.2/10. Published 2026-03-18.
- How severe is CVE-2026-31965?
- High severity. CVSS v3 base score is 8.2 out of 10.