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In jwt-simple 0.3.0 and earlier, the jwt.decode() function does not enforce the expected cryptographic algorithm when decoding JWTs. This allows an attacker to specify an arbitrary algorithm in the JWT header. If the server expects an asymmetric algorithm like RSA but receives a JWT signed with a symmetric algorithm like HMAC-SHA, and the server uses the RSA public key as the HMAC secret, the attacker can forge valid JWTs and impersonate users or escalate privileges.
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What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
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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Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
1 sources tracked across advisories and community write-ups. News coverage will land here when it surfaces.
No news coverage yet. Advisories and community discussion only.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.