How severe is CVE-2026-31962?

CVE-2026-31962 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-31962 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (28th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-31962?

CVE-2026-31962 primarily affects Htslib. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-31962?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-31962 have an EU (EUVD) identifier?

Yes. CVE-2026-31962 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-12923.

When was CVE-2026-31962 published?

CVE-2026-31962 was published on 2026-03-18 and last updated on 2026-06-17.

CVE-2026-31962

CVE-2026-31962 is a high-severity vulnerability in Htslib with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-122.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v4: 8.8
EPSS exploit prediction: 0% (28th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-12923
Weakness: CWE-122
Affected product: Htslib
Published: 2026-03-18
Last modified: 2026-06-17

Description

HTSlib is a library for reading and writing bioinformatics file formats. CRAM is a compressed format which stores DNA sequence alignment data. 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 `cram_decode_seq()` did not handle this correctly in some cases. Where this happened it could result in reading a single byte from beyond the end of a heap allocation, followed by writing a single attacker-controlled byte to the same location. 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.

Frequently asked questions

What is CVE-2026-31962?: HTSlib is a library for reading and writing bioinformatics file formats. CRAM is a compressed format which stores DNA sequence alignment data. 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 `cram_decode_seq()` did not handle this correctly in some cases. Where this happened it could result in reading a single byte from beyond the end of a heap allocation, followed by writing a single attacker-controlled byte to the same location. 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.
How severe is CVE-2026-31962?: CVE-2026-31962 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-31962 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (28th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-31962?: CVE-2026-31962 primarily affects Htslib. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-31962?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-31962 have an EU (EUVD) identifier?: Yes. CVE-2026-31962 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-12923.
When was CVE-2026-31962 published?: CVE-2026-31962 was published on 2026-03-18 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:htslib:htslib:*:*:*:*:*:*:*:*
cpe:2.3:a:htslib:htslib:1.23:*:*:*:*:*:*:*

More vulnerabilities in Htslib

CVE-2018-13845 — Critical (CVSS 9.8): An issue has been found in HTSlib 1.8. It is a buffer over-read in sam_parse1 in sam.c.
CVE-2017-1000206 — Critical (CVSS 9.8): samtools htslib library version 1.4.0 and earlier is vulnerable to buffer overflow in the CRAM rANS codec resulting in…
CVE-2026-31967 — Critical (CVSS 9.1): HTSlib is a library for reading and writing bioinformatics file formats. CRAM is a compressed format which stores DNA…
CVE-2026-31966 — Critical (CVSS 9.1): HTSlib is a library for reading and writing bioinformatics file formats. CRAM is a compressed format which stores DNA…
CVE-2020-36403 — High (CVSS 8.8): HTSlib through 1.10.2 allows out-of-bounds write access in vcf_parse_format (called from vcf_parse and vcf_read).
CVE-2026-31965 — High (CVSS 8.2): HTSlib is a library for reading and writing bioinformatics file formats. CRAM is a compressed format which stores DNA…

All CVEs affecting Htslib →

Other CWE-122 (Heap-based Buffer Overflow) vulnerabilities

CVE-2026-46752 — Critical (CVSS 10.0): Redis Lua HEAP overflow in cjson library vulnerability in Apache Kvrocks. This issue affects Apache Kvrocks: from…
CVE-2026-24822 — Critical (CVSS 10.0): Out-of-bounds Write, Heap-based Buffer Overflow vulnerability in ttttupup wxhelper (src modules). This vulnerability is…
CVE-2025-23123 — Critical (CVSS 10.0): A malicious actor with access to the management network could execute a remote code execution (RCE) by exploiting a…
CVE-2022-34819 — Critical (CVSS 10.0): A vulnerability has been identified in SIMATIC CP 1242-7 V2 (All versions < V3.3.46), SIMATIC CP 1243-1 (All versions <…
CVE-2026-44050 — Critical (CVSS 9.9): A heap-based buffer overflow in the CNID daemon comm_rcv() function in Netatalk 2.0.0 through 4.4.2 allows a remote…
CVE-2026-49841 — Critical (CVSS 9.8): FreeSWITCH is a Software Defined Telecom Stack enabling the digital transformation from proprietary telecom switches to…

Browse all CWE-122 (Heap-based Buffer Overflow) vulnerabilities →