Process abort via trailing percent format string
Published Feb 9, 2026 · Updated Feb 9, 2026
Heap out-of-bounds read in Janet 1.40.0 through 1.40.1 allows local users to abort a Janet process via a trailing percent format string. Within src/core/os.c, os_strftime advances past the final percent sign, accepts the terminating NUL through strchr, and reads one byte beyond the heap string. Executing attacker-controlled Janet code is required; the demonstrated consequence is an AddressSanitizer process abort, with no shown data disclosure.
Summary
What happened
Heap out-of-bounds read in Janet 1.40.0 through 1.40.1 allows local users to abort a Janet process via a trailing percent format string. Within src/core/os.c, os_strftime advances past the final percent sign, accepts the terminating NUL through strchr, and reads one byte beyond the heap string. Executing attacker-controlled Janet code is required; the demonstrated consequence is an AddressSanitizer process abort, with no shown data disclosure.
The record
- CVE
- CVE-2026-2241
- Published
- Feb 9, 2026
- Updated
- Feb 9, 2026
- Vendor
- Janet Language
- Product
- Janet
- Classifications
- CWE-125, CWE-119, T1499.004
- Attack vector
- local
- Privileges
- Unavailable
Timeline
How it unfolded
- Feb 9, 2026CVE publishedPublication date reported by the CVE source.
- Feb 9, 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?
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- Affected versionversion=1.40.0
- Affected versionversion=1.40.1
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
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
- Janet os_strftime reproducerproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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