Forge: X.509 basicConstraints bypass in verifyCertificateChain() via deprecated extension OIDs 2.5.29.10 and 2.5.29.13

Forge (also called node-forge) is a native implementation of Transport Layer Security in JavaScript. Prior to 1.4.1, node-forge parsed deprecated extension OIDs 2.5.29.10 and 2.5.29.13 as basicConstraints, and pki.verifyCertificateChain() used the first extension with that name. Exploitation requires a CA trusted by the application to issue a certificate carrying an attacker-supplied deprecated-OID extension, commonly because the CA copies extensions from a certificate signing request. By placing a permissive deprecated extension before the genuine 2.5.29.19 basicConstraints extension, the certificate holder could have the certificate accepted as a CA and issue certificates for arbitrary names, enabling server or client impersonation. If the issuing CA adds a keyUsage extension without keyCertSign, node-forge rejects the chain. This issue is fixed in version 1.4.1.

Source published

29 Oct 2026 19:25:09 UTC

Source modified

29 Oct 2026 20:25:04 UTC

Observed here

29 Oct 2026 21:48:56 UTC

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CVSS 3.1 · 7.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N