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CVE-2020-28042 is an authentication bypass vulnerability in ServiceStack affecting versions before 5.9.2. The flaw is caused by improper JWT signature verification, specifically acceptance of tokens with an invalid or effectively null signature unless the application implemented a custom ValidateToken function that enforced a valid minimum signature length. As a result, an attacker can forge arbitrary JWTs and have them accepted as authentic by applications relying on affected ServiceStack JWT authentication. Because JWT claims are commonly used to represent identity, session state, and authorization context, successful exploitation allows an attacker to submit attacker-controlled tokens that the application treats as valid.
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2 valid exploits after Mallory filtered fakes, detection scripts, and README-only repos.
Repository is a Python JWT security testing toolkit (“claimjumper”) rather than a single exploit for one product. It provides: (1) JWT decoding and vulnerability analysis with risk scoring (claimjumper/decoder.py, analyzer.py), (2) token forging (alg=none and HS256 with a provided secret) (forger.py), (3) multi-threaded HMAC secret brute forcing for HS256/384/512 using built-in/common secrets and optional wordlists (cracker.py plus wordlists/jwt_secrets.txt; also references a Wallarm wordlist path), (4) an “advanced_attacks” module that generates multiple CVE/pattern-based attack tokens (notably CVE-2022-39227 algorithm confusion, CVE-2018-0114 key injection, CVE-2022-21449 psychic signature, CVE-2020-28042 null signature bypass, plus kid/jku/x5u/jwks spoofing and timestamp tampering), (5) a fuzzing engine with payload libraries for path traversal, SQLi, NoSQLi, command injection, SSRF, etc. (fuzzer.py), and (6) optional live HTTP replay/testing and a playbook-style scanner using `requests` (http_tester.py) that can inject tokens into requests and look for canary/response changes; it logs to jwt_attack.log. The primary entry point is the Click-based CLI (claimjumper/cli.py) exposing commands like analyze, crack, forge/forge-none, advanced-attacks, fuzz, keygen, and full-audit. A standalone local HTML UI (jwt_analyzer.html) provides basic client-side decoding/forging guidance but does not itself perform signing. Overall purpose: generate and test malicious JWT variants against vulnerable JWT verification implementations and assist in auditing JWT configurations.
This repository is a Go-based operational exploit tool targeting JWT (JSON Web Token) vulnerabilities, including CVE-2015-9235, CVE-2016-10555, CVE-2018-0114, and CVE-2020-28042. The tool provides both command-line and interactive modes for penetration testers to generate and test JWTs against web applications. It supports multiple attack modes: modifying JWT headers (e.g., setting 'alg' to 'none'), exploiting missing signature validation, switching from RS256 to HS256, JWKS key injection, and brute-forcing JWT secrets using dictionaries or character sets. The tool can generate fuzzing dictionaries and outputs results to files for further testing. The codebase is organized into modules for command handling, JWT manipulation, brute-forcing, and utility functions. No hardcoded network endpoints are present, but several file paths are used for input/output. The exploit is mature and operational, providing practical attack payloads and automation for JWT vulnerability exploitation.
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2 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.