CVE-2026-31969
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.
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
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 High
CVSS: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 High
CVSS: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 High
CVSS: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 High
CVSS: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 High
CVSS: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 High
CVSS: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 High
CVSS: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 High
CVSS: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
| Package | Affected | Fixed |
|---|---|---|
htslibDebian: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 less1.19+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 |
htslibDebian: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 |
htslibDebian: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 |
htslibUbuntu:Pro:14.04:LTS |
All versions, plus listed versions 0.2.0~rc3-10.2.0~rc3-1ubuntu0.1~esm1 |
None known |
htslibUbuntu: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 |
htslibUbuntu: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 |
htslibUbuntu: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 |
htslibUbuntu:22.04:LTS |
All versions, plus listed versions 1.13+ds-21.13+ds-2build1 |
None known |
htslibUbuntu: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 |
htslibUbuntu:25.10 |
All versions, plus listed versions 1.21+ds-1 |
None known |
htslibUbuntu:26.10 |
All versions, plus listed versions 1.22.1+ds2-11.22.1+ds2-1build1 |
None known |
htslibUbuntu:26.04:LTS |
All versions, plus listed versions 1.21+ds-11.22.1+ds2-1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE 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
github.com/samtools/htslib/security/advisories/GHSA-q4cj-f4h5-fqgc
github.com/samtools/htslib/commit/88cdf69e4b83bb550ab4f6f7134892c2ad1978f4
github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31969.json
nvd.nist.gov/vuln/detail/CVE-2026-31969
security-tracker.debian.org/tracker/CVE-2026-31969
ubuntu.com/security/CVE-2026-31969
cve.org/CVERecord?id=CVE-2026-31969