# CVE-2026-31969: htslib: HTSlib is a library for reading and writing bioinformatics file formats

CVE-2026-31969 is fixed in htslib on 1 platform by DEBIAN-CVE-2026-31969 (version 1.24-2), released March 18, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-31969
- Priority: High
- CVSS: 8.1 (high)
- EPSS: 0.0036
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 18, 2026

## Description

HTSlib is a library for reading and writing bioinformatics file formats. CRAM is a compressed format which stores DNA sequence alignment data using a variety of encodings and compression methods.  When reading data encoded using the `BYTE_ARRAY_STOP` method, an out-by-one error in the `cram_byte_array_stop_decode_char()` function check for a full output buffer could result in a single attacker-controlled byte being written beyond the end of a heap allocation. 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | htslib Debian 14 | 1.24-2 | [DEBIAN-CVE-2026-31969](https://patchblox.com/security/data/fix/linux/debian-cve-2026-31969.md) | Mar 18, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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