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CVE-2026-31967

MEDIUM CVSS 4.0: 6.9 EPSS 0.02%
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-129 (Improper Validation of Array Index), CWE-125 (Out-of-bounds Read)
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. In the `cram_decode_slice()` function called while reading CRAM records, the value of the mate reference id field was not validated. Later use of this value, for example when converting the data to SAM format, could result in the out of bounds array reads when looking up the corresponding reference name.

If the array value obtained also happened to be a valid pointer, it would be interpreted as a string and an attempt would be made to write the data as part of the SAM record. This bug may allow information about program state to be leaked. It may also cause a program crash through an attempt 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.

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
Low
Partial data leak
Integrity
None
No 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:*:*:*:*:*:*:*