How severe is CVE-2026-31964?

CVE-2026-31964 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-31964 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (24th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-31964?

CVE-2026-31964 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-2026-31964?

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-2026-31964 have an EU (EUVD) identifier?

Yes. CVE-2026-31964 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-12932.

When was CVE-2026-31964 published?

CVE-2026-31964 was published on 2026-03-18 and last updated on 2026-06-17.

CVE-2026-31964

CVE-2026-31964 is a high-severity vulnerability in Htslib with a CVSS 3.x base score of 7.5. 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-476.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v4: 6.9
EPSS exploit prediction: 0% (24th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-12932
Weakness: CWE-476
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 using a variety of encodings and compression methods. 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 `CONST`, `XPACK` and `XRLE` encodings did not properly implement the interface needed to do this. Trying to decode records with omitted sequence or quality data using these encodings would result in an attempt to write to a NULL pointer. 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.

Frequently asked questions

What is CVE-2026-31964?: 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. 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 `CONST`, `XPACK` and `XRLE` encodings did not properly implement the interface needed to do this. Trying to decode records with omitted sequence or quality data using these encodings would result in an attempt to write to a NULL pointer. 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.
How severe is CVE-2026-31964?: CVE-2026-31964 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-31964 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (24th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-31964?: CVE-2026-31964 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-2026-31964?: 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-2026-31964 have an EU (EUVD) identifier?: Yes. CVE-2026-31964 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-12932.
When was CVE-2026-31964 published?: CVE-2026-31964 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-2026-31962 — High (CVSS 8.8): 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).

All CVEs affecting Htslib →

Other CWE-476 (NULL Pointer Dereference) vulnerabilities

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CVE-2020-14500 — Critical (CVSS 10.0): Secomea GateManager all versions prior to 9.2c, An attacker can send a negative value and overwrite arbitrary data.
CVE-2010-2495 — Critical (CVSS 10.0): The pppol2tp_xmit function in drivers/net/pppol2tp.c in the L2TP implementation in the Linux kernel before 2.6.34 does…
CVE-2026-46195 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: smb: client: validate dacloffset before building…
CVE-2026-31657 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: batman-adv: hold claim backbone gateways by…
CVE-2026-31436 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: dmaengine: idxd: fix possible wrong descriptor…

Browse all CWE-476 (NULL Pointer Dereference) vulnerabilities →