VulnerabilityPublished 10 Nov 2026

CVE-2026-120399: Red Hat Edge Manager 1 · Use of Blocking Code in Single-threaded, Non-blocking Context

Affects Red Hat Edge Manager 1Source CVE Database V5

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Not known to be exploited · CVSS 7.5 High.

Data as of 10 Nov 2026, 14:34 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.

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

Red Hat advises recovering affected services by restarting the server and blocking the malicious client at the network level. As a temporary workaround, scheduling recurrent checks on the listener's Recv-Q to terminate idle connections that have received almost no data can help mitigate the issue.

Description

CVE-2026-120399 is a vulnerability in Red Hat Edge Manager 1's flightctl component where a TLS handshake is 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, causing the affected listener to stop accepting new connections. Existing connections remain unaffected. The issue results in a denial of service (DoS) by resource exhaustion.

Impact

An unauthenticated attacker with network access can cause a denial of service by stalling the TLS handshake, which blocks the listener from accepting new connections. This impacts availability but does not compromise confidentiality or integrity. Existing connections remain unaffected during exploitation.

Summary

The vulnerability in flightctl involves a synchronous TLS handshake performed in a single-threaded, non-blocking context without a deadline, allowing an unauthenticated remote attacker with network access to stall the handshake. This stalls the listener and prevents it from accepting new incoming connections, effectively causing a denial of service. The flaw is tracked as CWE-1322 (Use of Blocking Code in Single-threaded, Non-blocking Context). The attack requires network access to the agent endpoint but does not affect existing connections. Red Hat has published an advisory detailing the issue and mitigation steps.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 10 Nov 2026, 14:34 UTC

Technical details

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