jsrsasign Cryptographic Implementation Flaws

The jsrsasign JavaScript cryptographic library contains a critical vulnerability in its random number generation functions that allows attackers to recover private DSA keys through nonce bias exploitation. Versions 7.0.0 through 11.1.0 are affected. A proof-of-concept is publicly available (referenced in GitHub Gist), demonstrating the attack feasibility, and the vulnerability requires no authentication or user interaction for remote exploitation.

Private key recovery is possible in jsrsasign versions before 11.1.1 when attackers force invalid DSA signatures with zero r or s values during the signing process. The library fails to validate or retry these malformed signatures, allowing attackers to algebraically solve for the private key x from the emitted signature. Publicly available exploit code exists demonstrating the key recovery technique (EPSS: 0.02%, percentile 5%), though no confirmed active exploitation. Vendor-released patch: version 11.1.1.

Cryptographic signature bypass in jsrsasign before 11.1.1 allows remote attackers to forge DSA signatures and X.509 certificates by supplying malicious domain parameters (g=1, y=1, r=1) that cause verification functions to incorrectly validate any message hash. This actively undermines authentication and integrity checks in applications using the library for JWT validation, certificate verification, or digital signatures. EPSS score is negligible (0.01%) despite proof-of-concept availability, and CISA SSVC classifies this as requiring proof-of-concept but not automatable, indicating targeted exploitation risk rather than widespread scanning.

The jsrsasign JavaScript library before version 11.1.1 contains a vulnerability that allows attackers to break signature verification by exploiting incorrect handling of negative exponents in modular exponentiation operations. This affects all versions prior to 11.1.1 of the jsrsasign package, enabling remote attackers without authentication to compromise cryptographic signature validation. A proof-of-concept exploit exists as indicated by the CVSS exploitability metric and public GitHub references demonstrating the attack technique.

The jsrsasign JavaScript library contains an infinite loop vulnerability in the BigInteger.modInverse function that allows remote attackers to permanently hang application processes through specially crafted zero or negative input values. All versions of jsrsasign prior to 11.1.1 are affected by this high-severity denial-of-service condition. A proof-of-concept exploit exists demonstrating the vulnerability, and the CVSS score of 7.5 reflects the ease of exploitation (network-accessible, low complexity, no authentication required).

jsrsasign versions before 11.1.1 contain a division by zero vulnerability in RSA public-key operations caused by improper parsing of JWK moduli that decode to zero. An attacker can supply a malicious JWK to force RSA verify and encryption operations to produce deterministic zero outputs while suppressing invalid key errors, leading to cryptographic bypass and information disclosure. A proof-of-concept exists and the vulnerability has moderate real-world risk due to its low attack complexity and local attack vector.