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CVE-2026-31969

HTSlib CRAM decoder has a heap buffer overflow

7.1 HighFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
Passive

What an attacker can affect

Confidentiality
None
Integrity
High
Availability
Low

Exploit likelihood

0.36%Up 0.3 points since Mar 19, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.1

HTSlib CRAM decoder has a heap buffer overflow

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.

Record
CVE-2026-31969
CVSS 4.0
7.1 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
Weakness
CWE-122, CWE-787
Updated
2026-11-02
EUVDEUVD-2026-12944 7.1

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.

Record
EUVD-2026-12944
CVSS 4.0
7.1 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
Updated
2026-11-02
NVD 7.1

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.

Record
CVE-2026-31969
CVSS 4.0
7.1 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/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
8.1 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H
Weakness
CWE-122, CWE-787
Updated
2026-11-02
OSV 7.1

HTSlib CRAM decoder has a heap buffer overflow

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.

Record
CVE-2026-31969
CVSS 4.0
7.1 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
Weakness
CWE-122, CWE-787
Updated
2026-11-02
OSVDEBIAN-CVE-2026-31969 8.1

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.

Record
DEBIAN-CVE-2026-31969
CVSS 3.1
8.1 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2026-31969 7.1

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.

Record
UBUNTU-CVE-2026-31969
CVSS 4.0
7.1 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N
CVSS 3.1
8.1 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
htslib
Debian:12
All versions, plus listed versions
1.16+ds-31.17+ds-0+exp11.17+ds-11.18+ds-0+exp11.18+ds-1
Show 15 moreShow less
1.19+ds-0+exp01.19+ds-11.19+ds-1+exp11.19+ds-1.11.20+ds-11.20+ds-21.21+ds-0+exp11.21+ds-0+exp21.21+ds-11.22.1+ds-11.22.1+ds-21.22.1+ds2-11.24-11.24-21.24-3
None known
htslib
Debian:13
All versions, plus listed versions
1.21+ds-11.22.1+ds-11.22.1+ds-21.22.1+ds2-11.24-11.24-21.24-3
None known
htslib
Debian:14
before 1.24-2, plus listed versions
1.21+ds-11.22.1+ds-11.22.1+ds-21.22.1+ds2-11.24-1
1.24-2
htslib
Ubuntu:Pro:14.04:LTS
All versions, plus listed versions
0.2.0~rc3-10.2.0~rc3-1ubuntu0.1~esm1
None known
htslib
Ubuntu:Pro:16.04:LTS
All versions, plus listed versions
1.2.1-11.2.1-21.2.1-2ubuntu11.2.1-2ubuntu1+esm1
None known
htslib
Ubuntu:Pro:18.04:LTS
All versions, plus listed versions
1.5-11.5-4ubuntu11.6-3ubuntu11.6-41.6-4build11.7-21.7-2ubuntu0.1~esm1
None known
htslib
Ubuntu:20.04:LTS
All versions, plus listed versions
1.9-101.9-111.9-121.10.2-2ubuntu11.10.2-2ubuntu21.10.2-31.10.2-3ubuntu0.1
None known
htslib
Ubuntu:22.04:LTS
All versions, plus listed versions
1.13+ds-21.13+ds-2build1
None known
htslib
Ubuntu:24.04:LTS
All versions, plus listed versions
1.17+ds-11.18+ds-11.19+ds-1.1build21.19+ds-1.1build3
None known
htslib
Ubuntu:25.10
All versions, plus listed versions
1.21+ds-1
None known
htslib
Ubuntu:26.10
All versions, plus listed versions
1.22.1+ds2-11.22.1+ds2-1build1
None known
htslib
Ubuntu:26.04:LTS
All versions, plus listed versions
1.21+ds-11.22.1+ds2-1
None known

History

History
RecordedChangedSources
first indexedCVE List, EUVD, NVD, OSV

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

In short

CVE-2026-31969 is a high vulnerability (CVSS 7.1) in Htslib, published March 18, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.36%, the 29th percentile. Fixed in htslib 1.24-2.

References

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