HTSlib is a library for reading and writing bioinformatics file formats. GZI files are used to index block-compressed GZIP [BGZF] files. In the GZI loading function, bgzf_index_load_hfile(), it was possible to trigger an integer overflow, leading to an under- or zero-sized buffer being allocated to store the index. Sixteen zero bytes would then be written to this buffer, and, depending on the result of the overflow the rest of the file may also be loaded into the buffer as well. If the function did attempt to load the data, it would eventually fail due to not reading the expected number of records, and then try to free the overflowed heap buffer. 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. The easiest work-around is to discard any .gzi index files from untrusted sources, and use the bgzip -r option to recreate them.
CVE-2026-31970
This high-severity CVE scores 8.1 under NVD CVSS v3. EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
- High severity, but no confirmed exploitation yet
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 8.1
- EG Score
- 8.1(low)
- EG Risk
- 41(Track)EG Risk 41/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity81% × 45%Exploitation0% × 40%Automatability30% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- —
- EPSS %ILE
- —
- KEV
- Not listed
Published
March 18, 2026
Last Modified
June 17, 2026
References (3)
- security-advisories@githubhttps://github.com/samtools/htslib/commit/6dd0d7d0e9e7e2e173a28969e624db8bc8bb5828
- security-advisories@githubhttps://github.com/samtools/htslib/security/advisories/GHSA-p345-84hx-fq6q
- af854a3a-2127-422b-91ae-364da2661108http://www.openwall.com/lists/oss-security/2026/03/18/9
Weakness Classification(5)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 2× in last 7d / 2× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-27 14:41 UTCEG score recompute
- 2026-07-27 14:27 UTCOSV refresh
Related CVEs(same CWE)
Same CWE
10 shownCWE-190 · CWE-787 · CWE-122
Frequently asked(4)
What is CVE-2026-31970?
When was CVE-2026-31970 disclosed?
What is the CVSS score of CVE-2026-31970?
How do I remediate CVE-2026-31970?
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-31970
Is Your Infrastructure Affected by CVE-2026-31970?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.