CVE-2026-31971
HTSlib CRAM decoder vulnerable to buffer overflow
CVE-2026-31971 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.
- Severity
- 7.1 HighCVSS 4.0, CVE List
- Exploit chance
- 0.36%EPSS, 29th percentile
- Exploitation
- None knownNot on CISA’s or ENISA’s lists
- Fixed in
1.24-2htslib +11 more
Description
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_LEN method, the cram_byte_array_len_decode() failed to validate that the amount of data being unpacked matched the size of the output buffer where it was to be stored. Depending on the data series being read, this could result either in a heap or a stack overflow with attacker-controlled bytes. Depending on the data stream this could result either in a heap buffer overflow or a stack overflow. If a user opens a file crafted to exploit this issue it could lead to the program crashing, overwriting of data structures on the heap or stack in ways not expected by the program, or changing the control flow of 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
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 |
What each source reports
CVE List Score used 7.1
HTSlib CRAM decoder vulnerable to 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_LEN method, the cram_byte_array_len_decode() failed to validate that the amount of data being unpacked matched the size of the output buffer where it was to be stored. Depending on the data series being read, this could result either in a heap or a stack overflow with attacker-controlled bytes. Depending on the data stream this could result either in a heap buffer overflow or a stack overflow. If a user opens a file crafted to exploit this issue it could lead to the program crashing, overwriting of data structures on the heap or stack in ways not expected by the program, or changing the control flow of 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-2026-31971- 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-121, CWE-122, CWE-787, CWE-1284
- Updated
- 2026-11-02
EUVDEUVD-2026-12948 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_LEN method, the cram_byte_array_len_decode() failed to validate that the amount of data being unpacked matched the size of the output buffer where it was to be stored. Depending on the data series being read, this could result either in a heap or a stack overflow with attacker-controlled bytes. Depending on the data stream this could result either in a heap buffer overflow or a stack overflow. If a user opens a file crafted to exploit this issue it could lead to the program crashing, overwriting of data structures on the heap or stack in ways not expected by the program, or changing the control flow of 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-2026-12948- 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_LEN method, the cram_byte_array_len_decode() failed to validate that the amount of data being unpacked matched the size of the output buffer where it was to be stored. Depending on the data series being read, this could result either in a heap or a stack overflow with attacker-controlled bytes. Depending on the data stream this could result either in a heap buffer overflow or a stack overflow. If a user opens a file crafted to exploit this issue it could lead to the program crashing, overwriting of data structures on the heap or stack in ways not expected by the program, or changing the control flow of 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-2026-31971- 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-121, CWE-122, CWE-787, CWE-1284
- Updated
- 2026-11-02
OSV 7.1
HTSlib CRAM decoder vulnerable to 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_LEN method, the cram_byte_array_len_decode() failed to validate that the amount of data being unpacked matched the size of the output buffer where it was to be stored. Depending on the data series being read, this could result either in a heap or a stack overflow with attacker-controlled bytes. Depending on the data stream this could result either in a heap buffer overflow or a stack overflow. If a user opens a file crafted to exploit this issue it could lead to the program crashing, overwriting of data structures on the heap or stack in ways not expected by the program, or changing the control flow of 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-2026-31971- 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-121, CWE-122, CWE-1284, CWE-787
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-31971 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_LEN method, the cram_byte_array_len_decode() failed to validate that the amount of data being unpacked matched the size of the output buffer where it was to be stored. Depending on the data series being read, this could result either in a heap or a stack overflow with attacker-controlled bytes. Depending on the data stream this could result either in a heap buffer overflow or a stack overflow. If a user opens a file crafted to exploit this issue it could lead to the program crashing, overwriting of data structures on the heap or stack in ways not expected by the program, or changing the control flow of 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-2026-31971- 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-2026-31971 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_LEN method, the cram_byte_array_len_decode() failed to validate that the amount of data being unpacked matched the size of the output buffer where it was to be stored. Depending on the data series being read, this could result either in a heap or a stack overflow with attacker-controlled bytes. Depending on the data stream this could result either in a heap buffer overflow or a stack overflow. If a user opens a file crafted to exploit this issue it could lead to the program crashing, overwriting of data structures on the heap or stack in ways not expected by the program, or changing the control flow of 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-2026-31971- 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
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
References
github.com/samtools/htslib/security/advisories/GHSA-jvx4-4wq7-6fmh
github.com/samtools/htslib/commit/01cd003b46fa2ebea4d9be5475b11217eb4c11be
github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31971.json
nvd.nist.gov/vuln/detail/CVE-2026-31971
security-tracker.debian.org/tracker/CVE-2026-31971
ubuntu.com/security/CVE-2026-31971
cve.org/CVERecord?id=CVE-2026-31971