---
title: CVE-2026-31965
description: Ubuntu is an open source software operating system that runs from the
  desktop, to the cloud, to all your internet connected things.
url: https://ubuntu.com/security/CVE-2026-31965
---

# CVE-2026-31965

Publication date 18 March 2026

Last updated 10 July 2026

---

Ubuntu priority

**Medium**

[Why this priority?](https://ubuntu.com/security/cves/about#priority )

## Cvss 3 Severity Score

**8.2 · High**

[Score breakdown](https://ubuntu.com/security/CVE-2026-31965#impact-score)

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## Description

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.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| htslib | 26.04 LTS resolute | Needs evaluation |
| 25.10 questing | Ignored end of life, was needs-triage |
| 24.04 LTS noble | Needs evaluation |
| 22.04 LTS jammy | Needs evaluation |
| 20.04 LTS focal | Needs evaluation |
| 18.04 LTS bionic | Needs evaluation |
| 16.04 LTS xenial | Needs evaluation |
| 14.04 LTS trusty | Needs evaluation |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)

## Severity score breakdown

CVSS version:

CVSS v4.0

[CVSS v4.0](https://ubuntu.com/security/CVE-2026-31965)
[CVSS v3.0](https://ubuntu.com/security/CVE-2026-31965)

**Base score**

6.9 · Medium

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | Low |
  | Attack requirements | None |
  | Privileges required | None |
  | User interaction | None |
  | Vulnerable system - Confidentiality impact | Low |
  | Vulnerable system - Integrity impact | None |
  | Vulnerable system - Availability impact | Low |
  | Subsequent system - Confidentiality impact | None |
  | Subsequent system - Integrity impact | None |
  | Subsequent system - Availability impact | None |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 6.9 · Medium |
  | Base + Threat score | - |
  | Base + Environmental score | - |
  | Base + Threat + Environmental score | - |

**Vector:** CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-31965)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-31965)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-31965)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2026-31965)

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2026-31965>
* <https://github.com/samtools/htslib/security/advisories/GHSA-mqm2-v645-3qhr>
* <https://github.com/samtools/htslib/commit/9cefb46453ad471e933b8212d4f45920524d3357>