Medium 4.4Published Oct 26, 2026

CVE-2026-116742HTSlib through 1.24 Heap Out-of-Bounds Write via Truncated .gzi Index Count

Updated under an hour ago (Oct 28, 2026, 6:50 PM ET)

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It affects samtools htslib. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for samtools htslib

Exploited in the last 30 days

HTSlib through 1.24 contains a heap out-of-bounds write and read vulnerability in bgzf_index_load_hfile() in bgzf.c that allows attackers to corrupt heap memory by supplying a crafted .gzi index entry count. A count of 0xFFFFFFFF truncates noffs to zero, causing writes past a malloc(0) buffer and an offs[-1] read in bgzf_useek(), resulting in heap corruption or crashes in tools like samtools and bcftools.

CVSS: 4.4 MEDIUM (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L
Weakness (CWE): CWE-197
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: VulnCheck
NVD analysis: Deferred
Record last updated: Oct 27, 2026
First seen by InfoSec Signals: Oct 26, 2026

Affected products

Affected products

samtools htslib samtools:htslib (from the name)	through 1.24	CNA record

References

References

https://github.com/samtools/htslib/pull/2057	issue-tracking, patch
https://github.com/samtools/htslib/commit/18dddf02bb2c0053b32acec427723555a24b2873	patch
https://github.com/samtools/htslib	product
https://github.com/samtools/htslib/blob/1.24/bgzf.c#L2504	technical-description
https://hackmd.io/@haindpwn/htslib-bgzf-gzi-int-truncation-oob	third-party-advisory
https://github.com/samtools/htslib/issues/2113	issue-tracking
https://www.vulncheck.com/advisories/htslib-through-1.24-heap-out-of-bounds-write-via-truncated-gzi-index-count	third-party-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.