CVE-2026-31973

NULL pointer dereference in samtools cram-size

6.9 MediumFix available

SAMtools is a program for reading, manipulating and writing bioinformatics file formats. Starting in version 1.17, in the cram-size command, used to write information about how well CRAM files are compressed, a check to see if the cram_decode_compression_header() was missing. If the function returned an error, this could lead to a NULL pointer dereference. 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 profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: Low
Availability: Low

Exploit likelihood

0.56%Up 0.5 points since Mar 19, 2026

What each source reports

CVE List Score used 6.9

NULL pointer dereference in samtools cram-size

Record: CVE-2026-31973
CVSS 4.0: 6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N
Weakness: CWE-476
Updated: 2026-11-02

EUVDEUVD-2026-12958 6.9

Record: EUVD-2026-12958
CVSS 4.0: 6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N
Updated: 2026-11-02

NVD 6.9

Record: CVE-2026-31973
CVSS 4.0: 6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/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
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-476
Updated: 2026-11-02

OSV 6.9

NULL pointer dereference in samtools cram-size

Record: CVE-2026-31973
CVSS 4.0: 6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N
Weakness: CWE-476
Updated: 2026-11-02

OSVDEBIAN-CVE-2026-31973 7.5

Record: DEBIAN-CVE-2026-31973
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-03

OSVUBUNTU-CVE-2026-31973 6.9

Record: UBUNTU-CVE-2026-31973
CVSS 4.0: 6.9 MediumCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

Affected products

samtools

Affected packages

Affected packages
Package	Affected	Fixed
`samtools` Debian:12	All versions, plus listed versions 1.16.1-11.17-0+exp11.17-11.18-11.19-1 Show 9 moreShow less 1.19.2-11.20-11.20-21.20-31.21-0+exp11.21-11.22.1-11.24-11.24-2	None known
`samtools` Debian:13	All versions, plus listed versions 1.21-11.22.1-11.24-11.24-2	None known
`samtools` Debian:14	before 1.24-2, plus listed versions 1.21-11.22.1-11.24-1	1.24-2
`samtools` Ubuntu:14.04:LTS	All versions, plus listed versions 0.1.19-1	None known
`samtools` Ubuntu:16.04:LTS	All versions, plus listed versions 0.1.19-1ubuntu1	None known
`samtools` Ubuntu:18.04:LTS	All versions, plus listed versions 1.4.1-1build11.5-1build11.6-3ubuntu11.6-41.7-1	None known
`samtools` Ubuntu:20.04:LTS	All versions, plus listed versions 1.9-41.9-51.9-61.9-71.10-3	None known
`samtools` Ubuntu:22.04:LTS	All versions, plus listed versions 1.13-21.13-4	None known
`samtools` Ubuntu:24.04:LTS	All versions, plus listed versions 1.17-11.18-11.19-11.19.2-11.19.2-1build11.19.2-1build2	None known
`samtools` Ubuntu:25.10	All versions, plus listed versions 1.21-1	None known
`samtools` Ubuntu:26.10	All versions, plus listed versions 1.22.1-1	None known
`samtools` Ubuntu:26.04:LTS	All versions, plus listed versions 1.21-11.22.1-1	None known

History

History
Recorded	Changed	Sources
Nov 3, 2026	affected, facts	OSV
Nov 2, 2026	first indexed	CVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-31973 is a medium vulnerability (CVSS 6.9) in Samtools, published March 18, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.56%, the 46th percentile. Fixed in samtools 1.24-2.