ajv has ReDoS when using `$data` option
ajv (Another JSON Schema Validator) through version 8.17.1 is vulnerable to Regular Expression Denial of Service (ReDoS) when the `$data` option is enabled. The pattern keyword accepts runtime data via JSON Pointer syntax (`$data` reference), which is passed directly to the JavaScript `RegExp()` constructor without validation. An attacker can inject a malicious regex pattern (e.g., `\"^(a|a)*$\"`) combined with crafted input to cause catastrophic backtracking. A 31-character payload causes approximately 44 seconds of CPU blocking, with each additional character doubling execution time. This enables complete denial of service with a single HTTP request against any API using ajv with `$data`: true for dynamic schema validation.
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2025-69873US | — | — | ||
ajv (Another JSON Schema Validator) before 8.18.0 is vulnerable to Regular Expression Denial of Service (ReDoS) when the $data option is enabled. The pattern keyword accepts runtim… | ||||
references
External citations — patches, advisories, analysis.
- https://github.com/EthanKim88/ethan-cve-disclosures/blob/main/CVE-2025-69873-ajv-ReDoS.mdWEB
- https://github.com/advisories/GHSA-2g4f-4pwh-qvx6ADVISORY
- https://github.com/ajv-validator/ajvPACKAGE
- https://github.com/ajv-validator/ajv/commit/720a23fa453ffae8340e92c9b0fe886c54cfe0d5WEB
- https://github.com/ajv-validator/ajv/pull/2586WEB
- https://github.com/ajv-validator/ajv/pull/2588WEB
- https://github.com/ajv-validator/ajv/pull/2590WEB
- https://github.com/ajv-validator/ajv/releases/tag/v6.14.0WEB
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