Memory corruption via unchecked CRAM decode length
Published Mar 18, 2026 · Updated Mar 18, 2026
Out-of-bounds writes in the CRAM decoder in Samtools HTSlib allow attackers to corrupt memory by supplying crafted CRAM files. The cram_byte_array_len_decode() function accepts BYTE_ARRAY_LEN output without verifying that the decoded byte count matches the destination buffer, allowing attacker-controlled bytes to overrun heap or stack storage. Opening a crafted file is required; exploitation can crash the calling process, overwrite heap or stack data, or redirect control flow.
Summary
What happened
Out-of-bounds writes in the CRAM decoder in Samtools HTSlib allow attackers to corrupt memory by supplying crafted CRAM files. The cram_byte_array_len_decode() function accepts BYTE_ARRAY_LEN output without verifying that the decoded byte count matches the destination buffer, allowing attacker-controlled bytes to overrun heap or stack storage. Opening a crafted file is required; exploitation can crash the calling process, overwrite heap or stack data, or redirect control flow.
The record
- CVE
- CVE-2026-31971
- Published
- Mar 18, 2026
- Updated
- Mar 18, 2026
- Vendor
- Samtools
- Product
- HTSlib
- Classifications
- CWE-121, CWE-1284, CWE-122, CWE-787, T1204.002, 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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