Red Hat CVE-2026-120399

A flaw was found in flightctl. A TLS handshake is performed synchronously in the HTTP server’s connection-context callback without a deadline. A network-reachable unauthenticated client can stall the handshake and prevent the affected listener from accepting new connections.

In order to exploit this flaw, an attacker must have network access to the agent endpoint; after exploitation, existing connections remain unaffected.

The services can be recovered by restarting the server and blocking the malicious device at network level. As a temporary workaround, you can schedule a recurrent check on the listener's Recv-Q; when the queue is non-zero, this terminates idle connections that have received almost no data.

Bugzilla 2564888 : flightctl-api: flightctl-remote-access: flightctl: Unbounded TLS handshake in ConnContext can block accepting connections

CWE-1322 : Use of Blocking Code in Single-threaded, Non-blocking Context

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

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

Understanding the Weakness (CWE)

Technical Impact: DoS: Resource Consumption (CPU)

When an attacker can directly invoke the blocking code, or the blocking code can be affected by environmental conditions that can be influenced by an attacker, then this can lead to a denial of service by causing unexpected hang or freeze of the code. An unexpected call to blocking code can trigger an infinite loop, or a large loop that causes the software to pause and wait indefinitely.

Red Hat would like to thank Miroslav Kolář (TSP Data) for reporting this issue.

Frequently Asked Questions

"Under investigation" doesn't necessarily mean that the product is affected by this vulnerability. It only means that our Analysis Team is still working on determining whether the product is affected and how it is affected.

The term 'Affected' means that our Analysis team has determined that this product, such as Red Hat Enterprise Linux 8 or OpenShift Container Platform 4, is affected by this vulnerability and a fix may be released to address this issue in the near future. This includes all minor releases of this product unless noted otherwise in the Statement text.

Upgrade to a supported product version that includes a fix for this vulnerability (recommended).

Apply a mitigation (if one exists).

Customers with the Technical Account Manager (TAM) RHEL Security Select Add-on can review this CVE directly with their TAM.

Apply a mitigation (if one exists).

Red Hat Engineering focuses on addressing high-priority issues based on the impact and product lifecycle expectations. Therefore, lower-priority issues will not receive immediate fixes.

Customers with the technical account manager (TAM) RHEL Security Select Add-on can review this CVE directly with their TAM.

Not sure what something means? Check out our Security Glossary .

For clarification or corrections, please Red Hat Product Security .