{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata. Fed continuously.","feed_url":"https://feed.craftedsignal.io/tags/nonce-bias/feed.json","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":[],"_cs_cpes":[],"_cs_cves":[],"_cs_exploited":false,"_cs_has_poc":false,"_cs_poc_references":[],"_cs_products":["jsrsasign"],"_cs_severities":["critical"],"_cs_tags":["jsrsasign","DSA","nonce-bias","cryptography","CVE-2026-4599"],"_cs_type":"advisory","_cs_vendors":["jsrsasign"],"content_html":"\u003cp\u003eThe jsrsasign library, a popular JavaScript cryptography toolkit, contains a critical vulnerability (CVE-2026-4599) in versions 7.0.0 up to, but not including, 11.1.1. This flaw resides in the \u003ccode\u003egetRandomBigIntegerZeroToMax\u003c/code\u003e and \u003ccode\u003egetRandomBigIntegerMinToMax\u003c/code\u003e functions within \u003ccode\u003esrc/crypto-1.1.js\u003c/code\u003e. The vulnerability stems from incomplete comparison checks that accept out-of-range candidates when generating DSA nonces. This introduces a bias in the nonce generation process, which an attacker could exploit to potentially recover the private key associated with the DSA signatures. This is a high-severity issue because successful exploitation allows for complete compromise of the cryptographic keys.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eAn attacker identifies a target application utilizing a vulnerable version (7.0.0 to 11.1.0) of the jsrsasign library for DSA signature generation.\u003c/li\u003e\n\u003cli\u003eThe application calls the vulnerable \u003ccode\u003egetRandomBigIntegerZeroToMax\u003c/code\u003e or \u003ccode\u003egetRandomBigIntegerMinToMax\u003c/code\u003e function within \u003ccode\u003esrc/crypto-1.1.js\u003c/code\u003e to generate a random nonce (\u003ccode\u003ek\u003c/code\u003e) for DSA signature creation.\u003c/li\u003e\n\u003cli\u003eDue to the incomplete comparison checks, the function generates a biased set of nonces, meaning some nonces are statistically more likely to be generated than others.\u003c/li\u003e\n\u003cli\u003eThe attacker collects a significant number of DSA signatures generated by the vulnerable application.\u003c/li\u003e\n\u003cli\u003eThe attacker analyzes the collected signatures, leveraging statistical analysis techniques to identify the bias in the generated nonces (\u003ccode\u003ek\u003c/code\u003e).\u003c/li\u003e\n\u003cli\u003eUsing the identified nonce bias, the attacker applies mathematical algorithms (e.g., lattice-based techniques or Hidden Number Problem solvers) to recover the private key.\u003c/li\u003e\n\u003cli\u003eThe attacker successfully reconstructs the private key used for signing.\u003c/li\u003e\n\u003cli\u003eThe attacker can now forge signatures, impersonate the legitimate entity, and potentially gain unauthorized access or perform malicious actions.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful exploitation of CVE-2026-4599 allows an attacker to recover the private key used in DSA signature generation by applications using vulnerable versions of jsrsasign. This allows the attacker to forge signatures, potentially leading to unauthorized access, data breaches, and complete compromise of systems relying on the affected keys. The vulnerability has a CVSS v3.1 base score of 9.1, indicating critical severity. While the number of victims is unknown, any application relying on jsrsasign for DSA signatures is potentially vulnerable.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eUpgrade the jsrsasign library to version 11.1.1 or later to patch CVE-2026-4599.\u003c/li\u003e\n\u003cli\u003eImplement the Sigma rule \u0026quot;Detect jsrsasign Vulnerable Version Usage\u0026quot; to identify systems using vulnerable versions of the library.\u003c/li\u003e\n\u003cli\u003eMonitor web server logs for requests containing potentially malicious DSA signature generation attempts, focusing on applications known to use jsrsasign.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2024-01-18T12:00:00Z","date_published":"2024-01-18T12:00:00Z","id":"https://feed.craftedsignal.io/briefs/2024-01-18-jsrsasign-dsa-nonce-bias/","summary":"jsrsasign versions 7.0.0 through 11.1.1 are vulnerable to a DSA nonce bias due to incomplete comparison checks in the getRandomBigIntegerZeroToMax and getRandomBigIntegerMinToMax functions, potentially allowing an attacker to recover the private key.","title":"jsrsasign DSA Nonce Bias Vulnerability (CVE-2026-4599)","url":"https://feed.craftedsignal.io/briefs/2024-01-18-jsrsasign-dsa-nonce-bias/"}],"language":"en","title":"CraftedSignal Threat Feed - Nonce-Bias","version":"https://jsonfeed.org/version/1.1"}