Heap corruption via off-by-one CRAM output check
Published Mar 18, 2026 · Updated Mar 18, 2026
Heap overflow in Samtools HTSlib before 1.21.1, 1.22 through 1.22.1, and 1.23 allows attackers to corrupt memory via a crafted CRAM file. The cram_byte_array_stop_decode_char() loop checks output capacity one byte late and copies an attacker-controlled byte past the heap allocation. Opening the file is required; the overflow can crash the process or corrupt adjacent heap data and structures.
Summary
What happened
Heap overflow in Samtools HTSlib before 1.21.1, 1.22 through 1.22.1, and 1.23 allows attackers to corrupt memory via a crafted CRAM file. The cram_byte_array_stop_decode_char() loop checks output capacity one byte late and copies an attacker-controlled byte past the heap allocation. Opening the file is required; the overflow can crash the process or corrupt adjacent heap data and structures.
The record
- CVE
- CVE-2026-31969
- Published
- Mar 18, 2026
- Updated
- Mar 18, 2026
- Vendor
- Samtools
- Product
- HTSlib
- Classifications
- CWE-787, CWE-122, 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
Compare your product and version with the public record. A matching version still requires validation against your environment.
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?
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.
Weakness, pattern, technique
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
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo