Oracle Database Protection Mechanism Bypass

Risk: Medium
Local: Yes
Remote: No
CWE: CWE-693

CVSS Base Score: 5.1/10
Impact Subscore: 6.4/10
Exploitability Subscore: 4.9/10
Exploit range: Remote
Attack complexity: High
Authentication: No required
Confidentiality impact: Partial
Integrity impact: Partial
Availability impact: Partial

Advisory ID: SYSS-2021-061 Product: Database Manufacturer: Oracle Affected Version(s):,, 19c Tested Version(s): 18c Vulnerability Type: Protection Mechanism Failure (CWE-693) Risk Level: High Solution Status: Fixed Manufacturer Notification: 2021-03-17 Solution Date: 2021-08-07 Public Disclosure: 2021-12-10 CVE Reference: CVE-2021-2351 Author of Advisory: Moritz Bechler, SySS GmbH ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Overview: Oracle Database is a general purpose relational database management system (RDMBS). The manufacturer describes the product as follows (see [1]): "Oracle database products offer customers cost-optimized and high-performance versions of Oracle Database, the world's leading converged, multi-model database management system, as well as in-memory, NoSQL and MySQL databases. Oracle Autonomous Database, available on premises via Oracle Cloud@Customer or in the Oracle Cloud Infrastructure, enables customers to simplify relational database environments and reduce management workloads." To protect the client/server communication, a proprietary security protocol "Native Network Encryption" (NNE) is used. A TLS-based alternative can optionally be configured. Due to insecure fallback behavior, a man-in-the-middle attacker can bypass NNE's protection against man-in-the-middle attacks and hijack authenticated connections. In some configurations, a full man-in-the-middle attack is possible. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Vulnerability Details: To mitigate against man-in-the-middle attacks on the initial Diffie- Hellman key exchange, the protocol implements the mixin of an additional shared key that is established by the authentication protocol (typically O5Logon). This relies on the fact that both client and server have knowledge of the user password (hash), which a potential attacker does not have. For more details on the protocol, refer to our paper [4]. SySS, however, found out that the JDBC Thin client implementation did not implement that fold-in and its connections were still accepted by database servers. The server performs a fallback to the initial session key if the decryption/integrity check fails. That original key is known to an attacker who has performed a classic man-in-the-middle attack against the initial Diffie-Hellman key exchange. For JDBC Thin client, this allows direct observation and manipulation of the application level traffic, as both parties still use the original keys. Nevertheless, other clients, which implement the authentication key fold-in, are still vulnerable. While the client expects a different session key after authentication has completed, it can simply be dropped/ignored. The server side of the connection at this point is already authenticated and communication is still possible due to the key fallback. This grants access to the database system as the original victim user. This attack is successful in all known configurations, except if TLS security is used. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Proof of Concept (PoC): For protocol analysis and attacks, SySS built a proxy server implementing the database protocol fundamentals and NNE. The proxy can perform a man-in-the-middle attack against the Diffie-Hellman key exchange during NNE negotation. Then, the necessary translation and adjustment between the client and server, which are now using different session keys, is performed. Launching the proxy and redirecting a client connection to it, the man-in-the-middle attack is performed. The encrypted part of the further protocol negotiation can be observed, including the authentication exchange. Then, the client is dropped, and the proxy sends a predefined query to the server. The following log excerpt shows an OCI client (21.3) connecting as the system user. The connection is hijacked and the system user table is queried by the attack proxy. > ./ --targethost --mitmDH --hijackConnection [...] |###[ Service ]### | serviceId = encryption | numParameters= 2 | unknown1 = 0 |###[ EncryptionResp ]### | version = 12000000 | algo = AES256 |###[ Service ]### | serviceId = integrity | numParameters= 8 | unknown1 = 0 |###[ IntegrityResp ]### | version = 12000000 | algo = SHA256 | len1 = 0800 | len2 = 0800 | generator = [...] | prime = [...] | public = [...] | rand = 666F6F206261722062617A206261742071757578 [...] DEBUG:root:Forward server -> client DEBUG:root:Received encrypted payload [...] [...]\x0cAUTH_USER_ID\x01\x00\x00\x00\x019\x00\x00\x00\x00\x0f\x00\x00\x00\x0fAUTH_SESSION_ID[...] [authentication completed at this point] INFO:root:Initially hijacking connection [...] DEBUG:root:Received encrypted payload [...] INFO:root:###[ TTIMsg ]### TTCode = 8 ###[ RPA ]### outNbPairs= None \nbPairs \ |###[ KVPair ]### | keyPtr = None | key = b'\x00VOracle Database 18c Express Edition Release - Production\nVersion' [...] INFO:root:b'[...]+select DISTINCT username FROM sys.all_users[...] INFO:root:Send encrypted payload [...] len 368 [...] DEBUG:root:Received encrypted payload [...] INFO:root:###[ TTIMsg ]### TTCode = 6 ###[ Raw ]### load = '[...]\x07\x06DBSNMP\x07\tAPPQOSSYS\x07\nGSMCATUSER\x07\x05GGSYS\x07\x03XDB[...]' ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Solution: Update the Oracle Database servers and clients to the patched versions. Enforce usage of a secured protocol version by setting the following options: SQLNET.ALLOW_WEAK_CRYPTO_CLIENTS=FALSE (server-side) SQLNET.ALLOW_WEAK_CRYPTO=FALSE (client-side) Or use TLS-based transport security instead of Native Network Encryption. More information: (customer account required) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Disclosure Timeline: 2021-03-02: Vulnerability discovered 2021-03-17: Vulnerability reported to manufacturer 2021-07-20: Initial patch release by manufacturer, 2021-08-07: Final patches released by manufacturer 2021-12-10: Public disclosure of vulnerability ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ References: [1] Product website for Oracle Database [2] SySS Security Advisory SYSS-2021-061 [3] SySS Responsible Disclosure Policy [4] Paper "Oracle Native Network Encryption" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Credits: This security vulnerability was found by Moritz Bechler of SySS GmbH. E-Mail: Public Key: Key ID: 0x768EFE2BB3E53DDA Key Fingerprint: 2C8F F101 9D77 BDE6 465E CCC2 768E FE2B B3E5 3DDA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Disclaimer: The information provided in this security advisory is provided "as is" and without warranty of any kind. Details of this security advisory may be updated in order to provide as accurate information as possible. The latest version of this security advisory is available on the SySS website. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Copyright: Creative Commons - Attribution (by) - Version 3.0 URL:

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