CVE-2026-12590
body-parser vulnerable to denial of service when invalid limit value silently disables size enforcement
Description
### Impact When body-parser is configured with an invalid `limit` option value, such as an unparseable string or `NaN`, `bytes.parse()` returns `null` and the request body size check is silently skipped. Applications that rely on `limit` as their primary safeguard against oversized request bodies will accept arbitrarily large payloads, leading to excessive memory and CPU usage and denial of service. This issue affects applications that pass a programmatically computed or user-configurable value to the `limit` option without validating it first. ### Patches This issue is fixed in [body-parser@2.3.0](https://github.com/expressjs/body-parser/releases/tag/v2.3.0) and [body-parser@1.20.6](https://github.com/expressjs/body-parser/releases/tag/v1.20.6) via [#698](https://github.com/expressjs/body-parser/pull/698). After the fix, invalid `limit` values throw a clear error at parser construction time instead of silently disabling enforcement. `null` and `undefined` continue to fall back to the default limit (`100kb`). ### Workarounds Validate `limit` before passing it to body-parser. For example, parse the value with [`bytes.parse()`](https://github.com/visionmedia/bytes.js) at startup and reject any configuration where it returns `null` or a non-finite number. ### References - [#698](https://github.com/expressjs/body-parser/pull/698): fix PR - [bytes.js](https://github.com/visionmedia/bytes.js): limit parser
How to fix CVE-2026-12590
To remediate CVE-2026-12590, upgrade the affected package to a fixed version below.
- —upgrade to 1.20.6 or later
Is CVE-2026-12590 being exploited?
Low — EPSS is 0.3%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- from 0, < 1.20.6