CVE-2026-31969

7.1 HIGH 0.4% exploit odds Fix listed Memory safety Library

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. 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.

At a glance

Exploitability: Can be exploited over the network without logging in, but needs a user to act. 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

2026-03-18 20:16 UTC PublishedDisclosed publicly on CVE.org and NVD
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: 7.1 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-122
Record status: Analyzed

Affected

Htslib < 1.21.1
Htslib < 1.22.2
Htslib 1.23

Attack profile CVSS 4.0 · 7.1

Attack vector: Network
Complexity: Low
Attack requirements: None
Privileges needed: None
User interaction: Passive
Confidentiality: None
Integrity: High
Availability: Low

Raw vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

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-2026-31969.md and follow it. Check whether this project is affected by CVE-2026-31969. 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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Fix and advisories

References

NVD record · CVE.org record