CVE-2019-20330
Description
A flaw was discovered in FasterXML jackson-databind, where it would permit polymorphic deserialization of malicious objects using the ehcache gadget when used in conjunction with polymorphic type handling methods such as enableDefaultTyping() or when @JsonTypeInfo is using Id.CLASS or Id.MINIMAL_CLASS or in any other way which ObjectMapper.readValue might instantiate objects from unsafe sources. An attacker could use this flaw to execute arbitrary code.
Statement
While OpenShift Container Platform's elasticsearch plugins do ship the vulnerable component, it doesn't do any of the unsafe things described in https://access.redhat.com/solutions/3279231. We may update the jackson-databind dependency in a future release.
Mitigation
The following conditions are needed for an exploit, we recommend avoiding all if possible:
* Deserialization from sources you do not control
* `enableDefaultTyping()`
* `@JsonTypeInfo using `id.CLASS` or `id.MINIMAL_CLASS`
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.1 | 9.8 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | High | Low | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | High | High | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Red Hat CVSS v3 Score Explanation
Red Hat Products do not enable the many conditions required for this flaw, and as such have a base score that differs from NVD's base evaluation, AC:L -> AC:H. This changed the base flaw impact as well, but does not alter individual product impacts.
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Application Data; Unexpected State
Attackers can modify unexpected objects or data that was assumed to be safe from modification. Deserialized data or code could be modified without using the provided accessor functions, or unexpected functions could be invoked.
Availability
Technical Impact: DoS: Resource Consumption (CPU)
If a function is making an assumption on when to terminate, based on a sentry in a string, it could easily never terminate.
Other
Technical Impact: Varies by Context
The consequences can vary widely, because it depends on which objects or methods are being deserialized, and how they are used. Making an assumption that the code in the deserialized object is valid is dangerous and can enable exploitation. One example is attackers using gadget chains to perform unauthorized actions, such as generating a shell.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
