CVE-2021-25329

Description

From CVE.org

The fix for CVE-2020-9484 was incomplete. When using Apache Tomcat 10.0.0-M1 to 10.0.0, 9.0.0.M1 to 9.0.41, 8.5.0 to 8.5.61 or 7.0.0. to 7.0.107 with a configuration edge case that was highly unlikely to be used, the Tomcat instance was still vulnerable to CVE-2020-9494. Note that both the previously published prerequisites for CVE-2020-9484 and the previously published mitigations for CVE-2020-9484 also apply to this issue.

Statement

In Red Hat Enterprise Linux 8, Red Hat Certificate System 10 and Identity Management are using the pki-servlet-engine component, which embeds a vulnerable version of Tomcat. However, in these specific contexts, the prerequisites to the vulnerability are not met. The PersistentManager is not set, and a SecurityManager is used. The use of pki-servlet-engine outside of these contexts is not supported. As a result, the vulnerability can not be triggered in supported configurations of these products.

Red Hat OpenStack Platform's OpenDaylight will not be updated for this flaw because it was deprecated as of OpenStack Platform 14 and is only receiving security fixes for Important and Critical flaws.

Mitigation

Users may configure the PersistenceManager with an appropriate value for sessionAttributeValueClassNameFilter to ensure that only application provided attributes are serialized and deserialized. For more details about the configuration, refer to the Apache Tomcat 9 Configuration Reference https://tomcat.apache.org/tomcat-9.0-doc/config/manager.html.

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 HatNVDcve.org
Base Score77N/A
Attack VectorLocalLocalN/A
Attack ComplexityHighHighN/A
Privileges RequiredLowLowN/A
User InteractionNoneNoneN/A
ScopeUnchangedUnchangedN/A
ConfidentialityHighHighN/A
Integrity ImpactHighHighN/A
Availability ImpactHighHighN/A

Vector

Red Hat: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

NVD: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Red Hat CVSS v3 Score Explanation

AV should be Local because the attacker requires a malicious file on a Tomcat server's local filesystem to exploit successfully.

AC should be High because there are sufficient factors beyond the attacker's control: a FileStore must be configured, PersistanceManager must have default value configured for sessionattributeclassnamefilter, local access and paths known. This set of conditions, we feel reflects AC:H rather than AC:L.

PR should be Low because the attacker requires to write privileges to a Tomcat server's filesystem but does not require significantly higher (e.g., administrative) permissions.

Understanding the Weakness (CWE)

CWE-502

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.

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