Memory disclosure or process termination via unbounded formatting
Published Apr 13, 2026 · Updated Apr 13, 2026
Out-of-bounds read in libjq through 1.8.1 allows remote attackers to disclose memory or terminate a consumer process via malformed JSON. The jv_parse_sized() error path passes the counted input to jv_string_fmt() with %s, so formatting continues beyond the supplied length until a NUL byte. Exploitation requires a libjq consumer to submit untrusted, malformed JSON in a non-NUL-terminated buffer; normal jq CLI paths use NUL-terminated strings.
Summary
What happened
Out-of-bounds read in libjq through 1.8.1 allows remote attackers to disclose memory or terminate a consumer process via malformed JSON. The jv_parse_sized() error path passes the counted input to jv_string_fmt() with %s, so formatting continues beyond the supplied length until a NUL byte. Exploitation requires a libjq consumer to submit untrusted, malformed JSON in a non-NUL-terminated buffer; normal jq CLI paths use NUL-terminated strings.
The record
- CVE
- CVE-2026-39979
- Published
- Apr 13, 2026
- Updated
- Apr 13, 2026
- Vendor
- jqlang
- Product
- jq
- Classifications
- CWE-125, T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 13, 2026CVE publishedPublication date reported by the CVE source.
- Apr 13, 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=< 2f09060afab23fe9390cce7cb860b10416e1bf5f
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Public exploit references
- poc_issue1_jv_parse_sized_oob.cproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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