7 CVE-2020-9484

When using Apache Tomcat versions 10.0.0-M1 to 10.0.0-M4, 9.0.0.M1 to 9.0.34, 8.5.0 to 8.5.54 and 7.0.0 to 7.0.103 if a) an attacker is able to control the contents and name of a file on the server; and b) the server is configured to use the PersistenceManager with a FileStore; and c) the PersistenceManager is configured with sessionAttributeValueClassNameFilter="null" (the default unless a SecurityManager is used) or a sufficiently lax filter to allow the attacker provided object to be deserialized; and d) the attacker knows the relative file path from the storage location used by FileStore to the file the attacker has control over; then, using a specifically crafted request, the attacker will be able to trigger remote code execution via deserialization of the file under their control. Note that all of conditions a) to d) must be true for the attack to succeed.
https://nvd.nist.gov/vuln/detail/CVE-2020-9484

Categories

CWE-502 : Deserialization of Untrusted Data
The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid. Marshaling and unmarshaling are effectively synonyms for serialization and deserialization, respectively. In Python, the "pickle" functionality is used to perform serialization and deserialization. Some PHP application researchers use this term when attacking unsafe use of the unserialize() function; but it is also used for CWE-915. Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.) If available, use the signing/sealing features of the programming language to assure that deserialized data has not been tainted. For example, a hash-based message authentication code (HMAC) could be used to ensure that data has not been modified. When deserializing data, populate a new object rather than just deserializing. The result is that the data flows through safe input validation and that the functions are safe. Explicitly define a final object() to prevent deserialization. Avoid having unnecessary types or gadgets available that can be leveraged for malicious ends. This limits the potential for unintended or unauthorized types and gadgets to be leveraged by the attacker. Add only acceptable classes to an allowlist. Note: new gadgets are constantly being discovered, so this alone is not a sufficient mitigation. chain: bypass of untrusted deserialization issue (CWE-502) by using an assumed-trusted class (CWE-183) Deserialization issue in commonly-used Java library allows remote execution. Deserialization issue in commonly-used Java library allows remote execution. Use of PHP unserialize function on untrusted input allows attacker to modify application configuration. Use of PHP unserialize function on untrusted input in content management system might allow code execution. Use of PHP unserialize function on untrusted input in content management system allows code execution using a crafted cookie value. Content management system written in PHP allows unserialize of arbitrary objects, possibly allowing code execution. Python script allows local users to execute code via pickled data. Unsafe deserialization using pickle in a Python script. Web browser allows execution of native methods via a crafted string to a JavaScript function that deserializes the string.

References

CPE

REMEDIATION

Patch

EXPLOITS

Exploit-db.com

POC Github

Other Nist (github, ...)

CAPEC

Common Attack Pattern Enumerations and Classifications

Cybersecurity needs ?

Strengthen software security from the outset with our DevSecOps expertise

Integrate security right from the start of the software development cycle for more robust applications and greater customer confidence.
Our team of DevSecOps experts can help you secure your APIs, data pipelines, CI/CD chains, Docker containers and Kubernetes deployments.

Discover this offer

Soutenez No Hack Me sur Tipeee