CVE-2026-118776 in forge
Summary
by MITRE • 10/29/2026
Forge (also called node-forge) is a native implementation of Transport Layer Security in JavaScript. Prior to 1.4.1, the affected implementation used decipher.finish(), CBC and ECB modes, PKCS#7 padding to process the relevant input or security decision. node-forge validated only the final byte of PKCS#7 padding during CBC and ECB decryption and accepted zero, oversized, or mismatched padding bytes. Malformed ciphertext could consequently be accepted and up to four plaintext blocks could be silently removed, causing an integrity failure in applications that treated successful decryption as proof of valid padding. This issue is fixed in version 1.4.1.
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Analysis
by VulDB Data Team • 10/29/2026
The node-forge library serves as a native implementation of Transport Layer Security protocols within the JavaScript ecosystem, enabling developers to handle cryptographic operations directly in client-side or server-side environments without relying on external system libraries. A critical security flaw was identified in versions prior to 1.4.1 regarding the handling of padding during decryption processes that utilize Cipher Block Chaining and Electronic Codebook modes with PKCS#7 padding schemes. The vulnerability stems from an insufficient validation mechanism within the decipher.finish() method, which is responsible for finalizing the decryption operation and removing applied padding structures before returning the plaintext data to the application layer.
The technical root cause of this flaw lies in the library's approach to verifying the integrity of PKCS#7 padded ciphertexts. According to standard cryptographic practices, when decrypting data encrypted with block ciphers using CBC or ECB modes, the final byte of each decrypted block indicates the number of padding bytes appended during encryption. A robust implementation must validate that all bytes constituting the padding match this indicated length and are non-zero where required by the specific mode's constraints. However, node-forge only inspected the very last byte of the padded data to determine validity. This partial validation allowed malformed ciphertexts containing zero-value padding bytes, oversized padding structures, or mismatched padding values to be accepted as valid inputs without triggering an error condition.
This inadequate verification logic leads directly to a significant integrity failure known as a padding oracle variant, specifically enabling silent truncation of plaintext data. Because the library did not reject invalid padding configurations strictly, attackers could manipulate ciphertext blocks such that up to four bytes of meaningful plaintext were silently removed during decryption while the application received no indication of tampering or corruption. In security-sensitive applications where successful decryption is implicitly treated as proof of message authenticity and integrity, this behavior creates a severe risk. An adversary with access to encrypted traffic can exploit this flaw to alter messages in transit, potentially modifying financial transactions, authentication tokens, or command structures without detection by the receiving application's standard error handling routines.
From an industry standards perspective, this vulnerability aligns closely with CWE-347 Improper Verification of Cryptographic Signature and CWE-697 Incorrect Comparison During Cryptographic Operations. The failure to strictly enforce padding integrity rules violates fundamental principles outlined in cryptographic best practices for ensuring data authenticity. Furthermore, the exploitation technique relates to ATT&CK tactic T1058 Resource Hijacking or potentially T1190 Exploit Public-Facing Application if leveraged within a broader attack chain involving man-in-the-middle scenarios where ciphertext manipulation occurs before decryption by vulnerable services. The silent removal of plaintext blocks effectively bypasses integrity checks, allowing for data tampering that remains undetected at the cryptographic layer.
The operational impact extends beyond simple data corruption to potential security breaches in systems relying on node-forge for secure communications. Applications using this library may inadvertently process modified commands or credentials if an attacker can predictably alter ciphertext blocks and exploit the padding validation weakness. This is particularly dangerous in protocols where message integrity is assumed upon successful decryption, such as certain implementations of TLS record layers or custom cryptographic APIs built atop node-forge. The lack of immediate feedback regarding invalid padding allows attackers to iteratively refine their inputs, potentially leading to more sophisticated attacks that compromise confidentiality and integrity simultaneously.
To mitigate this vulnerability, organizations utilizing node-forge must immediately upgrade to version 1.4.1 or later, where the padding validation logic has been corrected to strictly enforce PKCS#7 standards by checking all padding bytes rather than just the final one. For applications unable to update promptly due to dependency constraints, implementing additional integrity checks at the application layer is recommended. This includes using authenticated encryption modes such as GCM which inherently provide both confidentiality and integrity protection, thereby eliminating reliance on separate padding validation mechanisms. Additionally, developers should avoid manually handling raw CBC or ECB decryption with PKCS#7 padding in new codebases unless absolutely necessary, preferring higher-level abstractions that enforce correct cryptographic practices by default. Regular security audits of third-party cryptographic libraries are essential to ensure continued compliance with modern security standards and protection against evolving attack vectors targeting implementation flaws.