CVE-2026-11611
Description
A flaw was found in 389 Directory Server. The Content Synchronization persistent search plugin allows unbounded memory growth when an authenticated client stops reading sync responses, enabling denial of service. Additional race conditions in plugin thread lifecycle can cause crashes during connection teardown or shutdown.
Statement
Red Hat rates this issue as Moderate impact. The Content Synchronization persistent search plugin in 389-ds-base allows unbounded memory growth when an authenticated client opens a sync search and stops reading responses—modification events queue until memory exhaustion and server crash (confirmed on production binaries). Any authenticated user with search ACL access can trigger the primary denial-of-service path. Additional race conditions during connection teardown or shutdown can cause crashes on weak-memory-model architectures. These secondary paths have no configuration workaround.
Mitigation
Bug 1 (Queue DoS): Reduce SYNC_MAX_CONCURRENT from the default of 10 to minimize the number of clients that can accumulate queues. Apply network-level rate limiting on persistent sync search requests. Monitor client connections and terminate stalled sync clients that stop reading for an extended period. Set system-level memory limits (e.g., LimitAS= in the systemd unit file or cgroup memory limits) to prevent unbounded memory growth. Bugs 2 and 3: No workaround available — these are code-level race conditions that require source fixes.
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 | 6.5 | N/A | 6.5 |
| 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 | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Red Hat CVSS v3 Score Explanation
Primary Bug 1 (unbounded queue DoS): PR:L — any authenticated user with search ACL. Production confirmed UBI 8 + CentOS Stream 8.
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
If an attacker can trigger the allocation of the limited resources, but the number or size of the resources is not controlled, then the most common result is denial of service. This would prevent valid users from accessing the product, and it could potentially have an impact on the surrounding environment, i.e., the product may slow down, crash due to unhandled errors, or lock out legitimate users. For example, a memory exhaustion attack against an application could slow down the application as well as its host operating system.
Access Control,Other
Technical Impact: Bypass Protection Mechanism; Other
In some cases it may be possible to force the product to "fail open" in the event of resource exhaustion. The state of the product -- and possibly the security functionality - may then be compromised.
Acknowledgements
This issue was discovered by Ian Murphy (Red Hat).
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