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 `$data`: true for dynamic schema validation.
02 / AFFECTED SOFTWARE
Affected packages
123 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
ajv (Another JSON Schema Validator) through version 8.17.1 is vulnerable to Regular Expression Denial of Service (ReDoS) when the `$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.
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.
05 / REFERENCES
Further evidence
- https://github.com/EthanKim88/ethan-cve-disclosures/blob/main/CVE-2025-69873-ajv-ReDoS.md
- https://github.com/advisories/GHSA-2g4f-4pwh-qvx6
- https://github.com/ajv-validator/ajv
- https://github.com/ajv-validator/ajv/commit/720a23fa453ffae8340e92c9b0fe886c54cfe0d5
- https://github.com/ajv-validator/ajv/pull/2586
- https://github.com/ajv-validator/ajv/pull/2588
- https://github.com/ajv-validator/ajv/pull/2590
- https://github.com/ajv-validator/ajv/releases/tag/v6.14.0
- https://github.com/ajv-validator/ajv/releases/tag/v8.18.0
- https://github.com/github/advisory-database/pull/6991
- https://nvd.nist.gov/vuln/detail/CVE-2025-69873
- https://access.redhat.com/errata/RHSA-2026:10093
- https://access.redhat.com/errata/RHSA-2026:13512
- https://access.redhat.com/errata/RHSA-2026:14774
- https://access.redhat.com/errata/RHSA-2026:15091
- https://access.redhat.com/errata/RHSA-2026:16874
- https://access.redhat.com/errata/RHSA-2026:19712
- https://access.redhat.com/errata/RHSA-2026:26211
- https://access.redhat.com/errata/RHSA-2026:26214
- https://access.redhat.com/errata/RHSA-2026:33371
- https://access.redhat.com/errata/RHSA-2026:36651
- https://access.redhat.com/errata/RHSA-2026:40118
- https://access.redhat.com/errata/RHSA-2026:40945
- https://access.redhat.com/errata/RHSA-2026:40984
- https://access.redhat.com/errata/RHSA-2026:41941
- https://access.redhat.com/errata/RHSA-2026:41944
- https://access.redhat.com/errata/RHSA-2026:5168
- https://access.redhat.com/errata/RHSA-2026:5807
- https://access.redhat.com/errata/RHSA-2026:5907
- https://access.redhat.com/errata/RHSA-2026:5910
- https://access.redhat.com/errata/RHSA-2026:6192
- https://access.redhat.com/errata/RHSA-2026:6277
- https://access.redhat.com/errata/RHSA-2026:6309
- https://access.redhat.com/errata/RHSA-2026:6497
- https://access.redhat.com/errata/RHSA-2026:6567
- https://access.redhat.com/errata/RHSA-2026:6568
- https://access.redhat.com/errata/RHSA-2026:6802
- https://access.redhat.com/errata/RHSA-2026:7314
- https://access.redhat.com/errata/RHSA-2026:9742
- https://access.redhat.com/security/cve/CVE-2025-69873
- https://bugzilla.redhat.com/show_bug.cgi?id=2439070
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/69xxx/CVE-2025-69873.json
- https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-69873.json