body-parser vulnerable to denial of service when invalid limit value silently disables size enforcement

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 and body-parser@1.20.6 via #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() at startup and reject any configuration where it returns null or a non-finite number.

References

• #698: fix PR
• bytes.js: limit parser