Express.js body-parser up to 1.20.5/2.2.x Limit Validation bytes.parse limit denial of service

Summaryinfo

A vulnerability was found in Express.js body-parser up to 1.20.5/2.2.x. It has been classified as problematic. Affected by this vulnerability is the function bytes.parse of the component Limit Validation. This manipulation of the argument limit causes denial of service. The identification of this vulnerability is CVE-2026-12590. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability was found in Express.js body-parser up to 1.20.5/2.2.x. It has been declared as problematic. Affected by this vulnerability is the function bytes.parse of the component Limit Validation. The manipulation of the argument limit with an unknown input leads to a denial of service vulnerability. The CWE definition for the vulnerability is CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. As an impact it is known to affect availability. The summary by CVE is:

Impact: In body-parser versions prior to 1.20.6 (1.x line) and 2.3.0 (2.x line), when the 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. Patches: This issue is fixed in body-parser 1.20.6 and 2.3.0. After the fix, invalid limit values throw a clear error at parser construction time instead of silently disabling enforcement, while null and undefined continue to fall back to the default limit of 100kb. Workarounds: Validate the limit value before passing it to body-parser. For example, parse the value at startup and reject any configuration where the result is null or a non-finite number.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-12590 since 06/18/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 1.20.6 or 2.3.0 eliminates this vulnerability.

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Productinfo

Type

• JavaScript Library

Vendor

• Express.js

Name

• body-parser

Version

• 1.20.0
• 1.20.1
• 1.20.2
• 1.20.3
• 1.20.4
• 1.20.5
• 2.0
• 2.1
• 2.2

CPE 2.3info

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CPE 2.2info

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