Bug 2448756 (CVE-2026-31964)

Summary: CVE-2026-31964 htslib: HTSlib: Denial of Service via NULL pointer dereference in CRAM decoding
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedKeywords: Security
Target Milestone: ---   
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in HTSlib, a library for reading and writing bioinformatics file formats. When processing specially crafted CRAM (Compressed Reference-aligned Alignment Map) data, specifically records that omit sequence or quality data using the CONST, XPACK, or XRLE encodings, the library attempts to write to a NULL pointer. This NULL pointer dereference can cause the program to crash, leading to a Denial of Service (DoS).
 Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 2448821, 2448822, 2448823, 2448824, 2448825, 2448826    
Bug Blocks:    

Description OSIDB Bzimport 2026-03-18 19:03:29 UTC 
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.