CVE-2026-117680

jsv treats regex match budget exhaustion as a non-match, bypassing patternProperties and not

Published Nov 1, 2026 CVSS 4.0 · 2.1 Low EPSS < 1% KEV · Not listed
Description
Improper Check for Unusual or Exceptional Conditions vulnerability in the pattern and patternProperties keywords in lud jsv allows an unauthenticated remote attacker to bypass schema validation via a string that matches a schema regex only after heavy backtracking. JSV.Helpers.RegexExt.bounded_match?/2 runs schema regexes with a backtracking budget but calls :re.run/3 without :report_errors, so a match that exhausts the budget returns the same :nomatch as a real non-match. A key that matches a patternProperties regex is then checked against additionalProperties or not at all, and a string that matches a not subschema with a pattern is accepted. Before the budget existed, Regex.match?/2 failed the same way at Erlang's default match limit.

Only schemas whose regex explores a catastrophic branch before the branch that matches are affected. The attacker controls the data, not the schema, and linear patterns never exhaust the budget.

This issue affects jsv: from 0.1.0 before 0.26.2.

Remediation

Vendor Workaround

Pair patternProperties with additionalProperties: false. A key whose match exhausts the budget is then rejected instead of accepted unchecked. Valid keys that need heavy backtracking are rejected as well. Write schema regexes without nested quantifiers or overlapping alternatives, and do not express deny-lists as a not subschema with a pattern on untrusted input.

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description Improper Check for Unusual or Exceptional Conditions vulnerability in the pattern and patternProperties keywords in lud jsv allows an unauthenticated remote attacker to bypass schema validation via a string that matches a schema regex only after heavy backtracking. JSV.Helpers.RegexExt.bounded_match?/2 runs schema regexes with a backtracking budget but calls :re.run/3 without :report_errors, so a match that exhausts the budget returns the same :nomatch as a real non-match. A key that matches a patternProperties regex is then checked against additionalProperties or not at all, and a string that matches a not subschema with a pattern is accepted. Before the budget existed, Regex.match?/2 failed the same way at Erlang's default match limit. Only schemas whose regex explores a catastrophic branch before the branch that matches are affected. The attacker controls the data, not the schema, and linear patterns never exhaust the budget. This issue affects jsv: from 0.1.0 before 0.26.2.
Title jsv treats regex match budget exhaustion as a non-match, bypassing patternProperties and not
First Time appeared Lud
Lud jsv
Weaknesses CWE-754
CPEs cpe:2.3:a:lud:jsv:*:*:*:*:*:*:*:*
Vendors & Products Lud
Lud jsv
References
Metrics cvssV4_0

{'score': 2.1, 'vector': 'CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
EEF
Published
Updated
Nov 2, 2026, 7:44 PM
Reserved
Oct 30, 2026, 12:45 PM
Status
Deferred
Published
Nov 1, 2026, 2:18 PM
Modified
Nov 2, 2026, 8:17 PM