Ad

CVE-2026-31964

MEDIUM CVSS 4.0: 6.9 EPSS 0.06%
Updated Mar 19, 2026
Samtools
Parameter Value
CVSS 6.9 (MEDIUM)
Affected Versions 1.22 — 1.22.2
Fixed In 1.21.1
Type CWE-476 (NULL Pointer Dereference)
Vendor Samtools
Public PoC No

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. 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 `CONST`, `XPACK` and `XRLE` encodings did not properly implement the interface needed to do this. Trying to decode records with omitted sequence or quality data using these encodings would result in an attempt to write to a NULL pointer. Exploiting this bug causes a NULL pointer dereference.

Typically this will cause the program to crash. Versions 1.23.1, 1.22.2 and 1.21.1 include fixes for this issue. There is no workaround for this issue.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
None
No data leak
Integrity
Low
Partial data modification
Availability
Low
Partial disruption

CVSS Vector v4.0

Vulnerable Products 3

Configuration From (including) Up to (excluding)
Htslib Htslib
cpe:2.3:a:htslib:htslib:*:*:*:*:*:*:*:*
1.21.1
Htslib Htslib
cpe:2.3:a:htslib:htslib:*:*:*:*:*:*:*:*
1.22 1.22.2
Htslib Htslib
cpe:2.3:a:htslib:htslib:1.23:*:*:*:*:*:*:*