VulnerabilityPublished 10 Nov 2026

CVE-2026-120399: flightctl. A TLS handshake · CWE-1322

Source GCVE Database

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Authoritative record:CVE-2026-120399· High 7.5

Not known to be exploited · CVSS 7.5 High.

Data as of 10 Nov 2026, 18:03 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (redhat)	CVSS 3.1	7.5

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 10 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-9f6q-cw24-v4xv

What to do

Affected software

Product	Affected	Fixed in
Red Hat Edge Manager 1rhem/flightctl-api-rhel10	Affected–	Fixed in–
Red Hat Edge Manager 1rhem/flightctl-api-rhel9	Affected–	Fixed in–
Red Hat Edge Manager 1rhem/flightctl-remote-access-rhel10	Affected–	Fixed in–
Red Hat Edge Manager 1rhem/flightctl-remote-access-rhel9	Affected–	Fixed in–

AI-suggested

Mitigation involves restarting the affected server to recover service and blocking the malicious client at the network level. As a temporary workaround, administrators can schedule recurrent checks on the listener's Recv-Q and terminate idle connections that have received almost no data to prevent stalling. Monitor vendor advisories for updates on official fixes.

Description

A vulnerability in flightctl causes the TLS handshake to be performed synchronously without a deadline in the HTTP server's connection-context callback. This allows a network-reachable unauthenticated client to stall the handshake process, preventing the affected listener from accepting new connections and resulting in a denial of service. Existing connections remain unaffected after exploitation. Recovery requires restarting the server and blocking the malicious client at the network level. A temporary workaround involves monitoring the listener's Recv-Q and terminating idle connections.

Impact

The vulnerability allows an unauthenticated network attacker to cause a denial of service by stalling TLS handshakes, which blocks the affected listener from accepting new incoming connections. This results in availability impact without affecting confidentiality or integrity. Existing active connections are not disrupted by the attack.

Summary

CVE-2026-120399 describes a denial-of-service vulnerability in flightctl where the TLS handshake is executed synchronously in the HTTP server's connection-context callback without a deadline. An unauthenticated attacker with network access to the agent endpoint can stall the handshake, blocking the listener from accepting new connections. This flaw is categorized under CWE-1322 (Use of Blocking Code in Single-threaded, Non-blocking Context). The impact is availability loss due to resource consumption. The vulnerability does not affect confidentiality or integrity, and existing connections remain unaffected. Red Hat advisory provides mitigation steps but does not confirm an official patch release yet.

CWE-1322Use of Blocking Code in Single-threaded, Non-blocking Context (opens in a new tab)
Base weakness
The product uses a non-blocking model that relies on a single threaded process for features such as scalability, but it contains code that can block when it is invoked.
Implementation
Generally speaking, blocking calls should be replaced with non-blocking alternatives that can be used asynchronously. Expensive computations should be passed off to worker threads, although the correct approach depends on the framework being used.
Implementation
For expensive computations, consider breaking them up into multiple smaller computations. Refer to the documentation of the framework being used for guidance.
Attack patterns
Forced Deadlock (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 10 Nov 2026, 18:03 UTC

WeaknessesCWE-1322

Technical details

References

Community reviews

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