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CVE-2021-21424 is a user enumeration vulnerability in Symfony Security affecting switch user functionality. Due to different handling when attempting to switch to an existing versus a non-existing user, an attacker without the relevant permissions could distinguish whether a target username existed. The issue stemmed from observable differences in application behavior, including response handling and, per supporting advisory content, distinguishable exception messages and timing differences in related Guard/Authenticator authentication flows. Symfony addressed this by ensuring HTTP 403 responses are returned regardless of whether the target user exists when the requester is not authorized to switch users, including in the non-existent-user case. The patch referenced in the provided content is available for the 3.4 branch.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos (1 hidden).
This repository contains a proof-of-concept Python exploit for CVE-2021-21424, targeting the Symfony Web Profiler component. The exploit script (CVE-2021-21424.py) automates the process of enumerating available profiler tokens via the /_profiler/ endpoint and attempts to extract sensitive information (such as environment variables and internal paths) from each token's data. The README provides context about the vulnerability, affected versions (Symfony 2.8 to 5.x), and the risk of exposing the Web Profiler in production environments. The exploit requires the target to have the Web Profiler accessible over the network and is designed for information disclosure rather than remote code execution.
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2 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.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.