CVE-2026-84646
Description
A flaw was found in Jenkins. An attacker with Overall/Read permission can exploit a deserialization vulnerability where user objects can appear as nested field values in other deserialized XML objects. By submitting crafted XML, the attacker can create unauthorized user objects. While these created user objects are not actual Jenkins accounts and cannot be used for login, their unauthorized creation could lead to unexpected behavior or resource manipulation within the Jenkins environment.
Statement
This Moderate impact flaw in Jenkins allows authenticated attackers with Overall/Read permission to create unauthorized user objects through crafted XML deserialization. While these objects do not grant login capabilities nor expose confidential information, their creation could lead to unexpected resource manipulation within the Jenkins environment.
Mitigation
To mitigate this issue, restrict network access to the Jenkins instance to only trusted users and networks. Additionally, ensure that user permissions are configured with the principle of least privilege, limiting Overall/Read access to only those users who absolutely require it.
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).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.3 | N/A | 4.3 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | Low | N/A | Low |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
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
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