Staging Environment: Content and features may be unstable or change without notice.
Advisory details: ubuntu_osv / UBUNTU-CVE-2026-31969
Advisory ID ubuntu_osv/UBUNTU-CVE-2026-31969
Aliases CVE-2026-31969
Summary 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.
Status Published
Exploitability 0.5
Weighted Severity 7.3
Risk 3.6
Affected and Fixed Packages Package Details
Introduced and Fixed Package Commit Patches Package Commit Patches Details
Weaknesses (0)
There are no known CWE.
System Score Found at
cvssv3.1 8.1 https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-31969.json
cvssv4 7.1 https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-31969.json
ubuntu-priority medium https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-31969.json
Reference id Reference type URL
https://ubuntu.com/security/CVE-2026-31969
https://www.cve.org/CVERecord?id=CVE-2026-31969
88cdf69e4b83bb550ab4f6f7134892c2ad1978f4 Other https://github.com/samtools/htslib/commit/88cdf69e4b83bb550ab4f6f7134892c2ad1978f4
GHSA-q4cj-f4h5-fqgc Other https://github.com/samtools/htslib/security/advisories/GHSA-q4cj-f4h5-fqgc
No exploits are available.

No EPSS data available for this advisory.

Patch URL
There are no known patches.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H Found at https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-31969.json
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
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 Found at https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-31969.json
Attack Vector (AV) Attack Complexity (AC) Attack Requirements (AT) Privileges Required (PR) User Interaction (UI) Vulnerable System Impact Confidentiality (VC) Vulnerable System Impact Integrity (VI) Vulnerable System Impact Availability (VA) Subsequent System Impact Confidentiality (SC) Subsequent System Impact Integrity (SI) Subsequent System Impact Availability (SA)

network

adjacent

local

physical

low

high

none

present

none

low

high

none

passive

active

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

high

low

none

There are no SSVC decisions available.