CVE-2026-31970Network attack vector

Heap corruption via wrapped GZI allocation size

Published Mar 18, 2026 · Updated Mar 18, 2026

Heap buffer overflow in HTSlib before 1.21.1, 1.22 through 1.22.1, and 1.23 allows attackers to corrupt memory via a crafted GZI file. The bgzf_index_load_hfile() function trusts an index-supplied item count when computing allocation size; integer wraparound yields an undersized or zero-length heap buffer before at least 16 bytes and potentially more file data are written. Exploitation requires a user or user-initiated process to open the untrusted index, and the bounded observed consequence is a process crash or heap corruption; arbitrary code execution is unconfirmed.

CVSS severity7.1
High
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap buffer overflow in HTSlib before 1.21.1, 1.22 through 1.22.1, and 1.23 allows attackers to corrupt memory via a crafted GZI file. The bgzf_index_load_hfile() function trusts an index-supplied item count when computing allocation size; integer wraparound yields an undersized or zero-length heap buffer before at least 16 bytes and potentially more file data are written. Exploitation requires a user or user-initiated process to open the untrusted index, and the bounded observed consequence is a process crash or heap corruption; arbitrary code execution is unconfirmed.

The record

CVE
CVE-2026-31970
Published
Mar 18, 2026
Updated
Mar 18, 2026
Vendor
Samtools
Product
HTSlib
Classifications
CWE-787, CWE-122, CWE-1284, CWE-190, CWE-131, T1204.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.21.1
  2. Affected versionversion=>= 1.22, < 1.22.2
  3. Affected versionversion== 1.23

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Samtools · HTSlibversion=< 1.21.1; version=>= 1.22, < 1.22.2; version== 1.23

Published CVSS scores

7.1GitHub, Inc.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
8.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
CWE-122Heap-based Buffer Overflow
CWE-1284Improper Validation of Specified Quantity in Input
CWE-190Integer Overflow or Wraparound
CWE-131Incorrect Calculation of Buffer Size
T1204.002User Execution: Malicious File

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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