CVE-2026-31968

What it is

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. For the `VARINT` and `CONST` encodings, incomplete validation of the context in which the encodings were used could result in up to eight bytes being written beyond the end of a heap allocation, or up to eight bytes being written to the location of a one byte variable on the stack, possibly causing the values to adjacent variables to change unexpectedly. Depending on the data stream this could result either in a heap buffer overflow or a stack overflow. If a user opens a file crafted to exploit this issue it could lead to the program crashing, overwriting of data structures on the heap or stack in ways not expected by the program, or changing the control flow of 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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data tampering.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-03-18 20:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 10:34 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.4% in the next 30 days (EPSS).
• Severity: 8.8 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-03-18 20:16 UTC

Last modified

2026-06-17 10:34 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-121

Record status

Analyzed

Affected

• Htslib < 1.21.1
• Htslib < 1.22.2
• Htslib 1.23

Attack profile CVSS 4.0 · 8.8

Attack vector

Network

Complexity

Low

Attack requirements

None

Privileges needed

None

User interaction

None

Confidentiality

None

Integrity

High

Availability

Low

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-31968.md and follow it. Check whether this project is affected by CVE-2026-31968. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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