CVE-2025-69873: ajv has ReDoS when using `$data` option

Severity: low (CVSS 2.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-02-11 · updated 2026-09-10
Weakness: CWE-1333

Description

ajv (Another JSON Schema Validator) before 8.18.0 is vulnerable to Regular Expression Denial of Service (ReDoS) when the $data option is enabled. The pattern keyword accepts runtime data via JSON Pointer syntax ($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. This issue is also fixed in version 6.14.0.

Affected products

Npm Ajv: from 7.0.0-alpha.0 before 8.18.0; before 6.14.0 — fixed in 8.18.0, 6.14.0
ajv.js ajv: before 6.14.0; from 7.0.0 before 8.17.2 — fixed in 6.14.0, 8.17.2

How to fix

Upgrade to a fixed version: Npm Ajv 8.18.0, 6.14.0; ajv.js ajv 6.14.0, 8.17.2. Check the vendor advisory for mitigations.

References

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