Vulnerabilities

Security fix · CVE-2026-119186

Forge: AES-GCM authentication bypass via unvalidated tagLength option

Published Oct 30, 2026 · catalog updated Oct 30, 2026 · Forge: AES-GCM authentication bypass

Last checked Nov 6, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-119186. EPSS is 0.21%. Act only if a listed version of Forge: AES-GCM authentication bypass is installed.

Severity

Medium5.9

Known exploitation

Not in CISA/VulnCheck KEV

EPSS

0.21%

Remediation

Version ranges on file

Affected products

npm node-forge

### Summary The AES-GCM mode in forge.cipher does not validate the tagLength option passed to start(). With a tagLength of 0 or a value that converts to 0 (such as null, false, '' or '0'), the authentication tag is empty, and decipher.finish() returns true for any ciphertext and additional data when the supplied tag is empty or missing. Fixed in node-forge 1.4.1. ### Details in stored the option without validation, and documented it as accepting "0-128". After processing the data, truncates the 16-byte tag with . For a that converts to 0, this is , and truncating by empties the tag. On decryption, the start-time check that the supplied has bytes passes for an empty tag, and the final tag comparison compares two empty strings, so returns for any ciphertext and additional data. NIST SP 800-38D section 5.2.1.2 allows only tag lengths of 128, 120, 112, 104 and 96 bits, plus 64 and 32 bits for certain applications. The fix validates in , for both encryption and decryption. A missing, or uses the default of 128 bits. Any other value is converted with and must be one of 128, 120, 112, 104, 96, 64 or 32; otherwise throws "Invalid tag length.". Numeric strings such as are still accepted. With a validated , an empty tag no longer matches the expected tag length and is rejected. ### Patches Fixed in node-forge 1.4.1. now throws an error unless is one of the tag lengths allowed by NIST SP 800-38D (128, 120, 112, 104, 96, 64 or 32 bits); a or means the default of 128 bits. ### Workarounds Do not derive from received data. Pass a fixed (or omit it to use the default of 128 bits), and check that the received tag has the expected length before calling , for example before . ### Proof of concept Start an AES-GCM decipher with and an empty tag, as an application does when it derives the tag length from a received empty tag, and feed it arbitrary bytes that were never encrypted under the key: values , and (with an empty tag), and with no option, give the same result on <= 1.4.0. The f