Heap corruption via zero-length CRAM record writes
Published Mar 18, 2026 · Updated Mar 18, 2026
Heap buffer overflow in Samtools HTSlib allows attackers to corrupt heap memory through a crafted CRAM file processed by an application. In cram_decode_seq(), records with no stored sequence still trigger sequence or quality writes after dummy CRAM data is consumed, causing a one-byte read and attacker-controlled write past the heap allocation. Processing the file is required; exploitation can crash the consuming process or corrupt heap data and structures, while arbitrary code execution is unconfirmed.
Summary
What happened
Heap buffer overflow in Samtools HTSlib allows attackers to corrupt heap memory through a crafted CRAM file processed by an application. In cram_decode_seq(), records with no stored sequence still trigger sequence or quality writes after dummy CRAM data is consumed, causing a one-byte read and attacker-controlled write past the heap allocation. Processing the file is required; exploitation can crash the consuming process or corrupt heap data and structures, while arbitrary code execution is unconfirmed.
The record
- CVE
- CVE-2026-31962
- Published
- Mar 18, 2026
- Updated
- Mar 18, 2026
- Vendor
- Samtools
- Product
- HTSlib
- Classifications
- CWE-125, CWE-787, CWE-129, CWE-122, T1203
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 18, 2026CVE publishedPublication date reported by the CVE source.
- 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.
- Affected versionversion=< 1.21.1
- Affected versionversion=>= 1.22, < 1.22.2
- Affected versionversion== 1.23
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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