# CVE-2026-31962: htslib: HTSlib is a library for reading and writing bioinformatics file formats

CVE-2026-31962 is fixed in 12 products on 1 platform, first by DEBIAN-CVE-2026-31962, released March 18, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-31962
- Priority: High
- CVSS: 8.8 (high)
- EPSS: 0.0038
- 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. While most alignment records store DNA sequence and quality values, the format also allows them to omit this 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | bcftools Fedora 43 | 1.23.1-1.fc43 | [FEDORA-2026-3B06345BF2](https://patchblox.com/security/data/fix/linux/fedora-2026-3b06345bf2.md) | Mar 19, 2026 |
| Linux | bcftools-debuginfo Fedora 43 | 1.23.1-1.fc43 | [FEDORA-2026-3B06345BF2](https://patchblox.com/security/data/fix/linux/fedora-2026-3b06345bf2.md) | Mar 19, 2026 |
| Linux | bcftools-debugsource Fedora 43 | 1.23.1-1.fc43 | [FEDORA-2026-3B06345BF2](https://patchblox.com/security/data/fix/linux/fedora-2026-3b06345bf2.md) | Mar 19, 2026 |
| Linux | htslib Debian 14 | 1.24-2 | [DEBIAN-CVE-2026-31962](https://patchblox.com/security/data/fix/linux/debian-cve-2026-31962.md) | Mar 18, 2026 |
| Linux | htslib Fedora 43 | 1.23.1-1.fc43 | [FEDORA-2026-3B06345BF2](https://patchblox.com/security/data/fix/linux/fedora-2026-3b06345bf2.md) | Mar 19, 2026 |
| Linux | htslib-debuginfo Fedora 43 | 1.23.1-1.fc43 | [FEDORA-2026-3B06345BF2](https://patchblox.com/security/data/fix/linux/fedora-2026-3b06345bf2.md) | Mar 19, 2026 |
| Linux | htslib-debugsource Fedora 43 | 1.23.1-1.fc43 | [FEDORA-2026-3B06345BF2](https://patchblox.com/security/data/fix/linux/fedora-2026-3b06345bf2.md) | Mar 19, 2026 |
| Linux | htslib-devel Fedora 43 | 1.23.1-1.fc43 | [FEDORA-2026-3B06345BF2](https://patchblox.com/security/data/fix/linux/fedora-2026-3b06345bf2.md) | Mar 19, 2026 |
| Linux | htslib-tools Fedora 43 | 1.23.1-1.fc43 | [FEDORA-2026-3B06345BF2](https://patchblox.com/security/data/fix/linux/fedora-2026-3b06345bf2.md) | Mar 19, 2026 |
| Linux | htslib-tools-debuginfo Fedora 43 | 1.23.1-1.fc43 | [FEDORA-2026-3B06345BF2](https://patchblox.com/security/data/fix/linux/fedora-2026-3b06345bf2.md) | Mar 19, 2026 |
| Linux | samtools Fedora 43 | 1.23.1-1.fc43 | [FEDORA-2026-3B06345BF2](https://patchblox.com/security/data/fix/linux/fedora-2026-3b06345bf2.md) | Mar 19, 2026 |
| Linux | samtools-debuginfo Fedora 43 | 1.23.1-1.fc43 | [FEDORA-2026-3B06345BF2](https://patchblox.com/security/data/fix/linux/fedora-2026-3b06345bf2.md) | Mar 19, 2026 |
| Linux | samtools-debugsource Fedora 43 | 1.23.1-1.fc43 | [FEDORA-2026-3B06345BF2](https://patchblox.com/security/data/fix/linux/fedora-2026-3b06345bf2.md) | Mar 19, 2026 |

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Data as of 2026-11-09T01:18:40Z 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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