CVE-2026-103877
Description
A flaw was found in Apache Directory LDAP API. When a client calls loadSchema() to search an LDAP server's subschema, a rogue or compromised server, or a network attacker able to intercept the connection before TLS is established, can return a crafted schema object containing a serialized Java class. Processing this response can trigger unsafe deserialization and may allow arbitrary code execution in the client application. Apache Directory LDAP API versions 2.1.0 through versions before 2.1.9 are affected; version 2.1.9 fixes the issue.
Statement
This vulnerability is rated as Important severity because successful exploitation could permit arbitrary code execution within the context of the running client application. The risk is reduced from Critical because exploitation demands specific preconditions: the client must initiate schema discovery queries, and an attacker must either control the target directory service or perform a man-in-the-middle attack prior to transport encryption. Red Hat products shipping earlier major versions of the library, such as 1.x, do not contain the affected functionality.
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 | 8.1 | N/A | 9.8 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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.
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