ajv has ReDoS when using $data option

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

5.5 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P · score source

EPSS

• CVE-2025-69873: 0.55% estimated exploitation activity in the next 30 days; percentile 45.88 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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.

Published by the source

11 Feb 2026, 21:30 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:42 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-2g4f-4pwh-qvx6

2. Revision 2 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-2g4f-4pwh-qvx6

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# Patch Next advisory brief: CVE-2025-69873

Advisory: ajv has ReDoS when using `$data` option
IDs: CVE-2025-69873, GHSA-2g4f-4pwh-qvx6
Record: https://patchnext.com/advisories/cve-2025-69873 (revision 3, source checked 26 Oct 2026, 12:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: ajv 8.18.0, 6.14.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm ajv: affected >= 7.0.0-alpha.0, < 8.18.0; < 6.14.0; fixed in 6.14.0, 8.18.0

## Suggested inspection (read-only)
- `npm ls ajv --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on ajv.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-2g4f-4pwh-qvx6 (OSV record GHSA-2g4f-4pwh-qvx6 lists affected ranges: npm ajv >=7.0.0-alpha.0 =0 <6.14.0 (fixed))
- Verified: https://github.com/advisories/GHSA-2g4f-4pwh-qvx6 (GitHub-reviewed advisory GHSA-2g4f-4pwh-qvx6 lists affected ranges: npm ajv >=7.0.0-alpha.0 =0 <6.14.0)

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