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CVE-2021-31196 is a Microsoft Exchange Server vulnerability in Outlook Web Access Form-Based Authentication cookie parsing, commonly identified as part of the ProxyOracle attack chain. Exchange processes AES-CBC-encrypted credential data stored in FBA cookies and returns distinguishable redirect responses when decryption fails due to invalid padding versus when padding is valid but the resulting credentials fail authentication. This observable response discrepancy creates a padding oracle, enabling an attacker to iteratively decrypt captured encrypted credential-cookie data. Microsoft classified the vulnerability as an Important remote code execution issue requiring high privileges.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository contains operational exploit scripts for multiple high-profile Microsoft Exchange Server vulnerabilities: ProxyLogon (CVE-2021-26855, etc.), ProxyOracle (CVE-2021-31196), and ProxyShell (CVE-2021-34473, CVE-2021-31207). The structure includes four main Python scripts: - 26855.py: Implements the ProxyLogon exploit chain, culminating in the upload of a JScript webshell (api.aspx) to the Exchange server by abusing the OAB virtual directory. It automates the process of obtaining necessary tokens and SIDs, and provides a final webshell URL for remote code execution. - 31196.py: Implements the ProxyOracle padding oracle attack, allowing extraction of plaintext credentials from encrypted session cookies by exploiting a padding oracle vulnerability in OWA. It requires a valid 'cadata' cookie and outputs the decrypted username and password. - 34473.py: Implements the ProxyShell exploit chain, allowing remote PowerShell command execution on the Exchange server. It automates the process of obtaining a valid CommonAccessToken and then uses pypsrp to execute arbitrary PowerShell scripts remotely. - 31207.py: Works with 34473.py to deliver arbitrary files (e.g., malicious PDFs) to user mailboxes and then exports mailbox contents to a specified UNC path, leveraging Exchange's mailbox export features. A users.txt file provides a list of default or known usernames to assist in the exploitation process. The README.md gives usage instructions and references for each exploit. The scripts are operational and automate the full exploitation process, including credential extraction, webshell upload, remote command execution, and file delivery. The main attack vector is network-based, targeting exposed Exchange web services (ECP, OWA, Autodiscover, EWS, and PowerShell endpoints).
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A padding-oracle vulnerability in Microsoft Exchange Form-Based Authentication cookie processing. Distinct responses for invalid AES-CBC padding versus failed authentication provide an oracle that can decrypt captured cadata cookies and recover users' plaintext passwords, except for a small portion of the username field.
A Microsoft Exchange vulnerability that is part of the ProxyOracle attack chain.
A Microsoft Exchange Server vulnerability identified as part of ProxyOracle, an attack described as capable of recovering Exchange users' passwords in plaintext.
Microsoft Exchange Server remote code execution vulnerability addressed in Microsoft's July updates.
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.