CVE-2026-21914VulnerabilityPublished 15 Jan 2026

CVE-2026-21914: Juniper Networks Junos OS · Improper Locking

Affects Juniper Networks Junos OSSource CVE Database V5

Not known to be exploited · CVSS 7.5 High · fixed in 25.2R1-S1 : patch Juniper Networks Junos OS soon.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 24% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 25.2R1-S1, 24.4R2-S2, 24.2R2-S3 +3

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 15 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 2026-10-26.

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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC 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

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
Juniper NetworksJunos OS	Affected <22.4R3-S8 >=23.2 <23.2R2-S5 >=23.4 <23.4R2-S6 >=24.2 <24.2R2-S3 >=24.4 <24.4R2-S2 =25.2	Fixed in 25.2R1-S1 24.4R2-S2 24.2R2-S3 23.4R2-S6 23.2R2-S5 22.4R3-S8

AI-suggested

European organizations should immediately identify all Juniper SRX Series devices running affected Junos OS versions and prioritize patching to the fixed releases listed by Juniper Networks. Network administrators should apply the updates: 22.4R3-S8 or later, 23.2R2-S5 or later, 23.4R2-S6 or later, 24.2R2-S3 or later, 24.4R2-S2 or later, and 25.2R1-S1 or later. If you cannot patch yet, organizations should implement network-level mitigations such as filtering or rate-limiting GTP Modify Bearer Request messages from untrusted or external sources to reduce exposure. Monitoring network traffic for anomalous or malformed GTP messages can help detect attempted exploitation. Employing intrusion detection/prevention systems (IDS/IPS) with updated signatures targeting this vulnerability is recommended. Additionally, segmenting critical network infrastructure and restricting access to management interfaces can limit the attack surface. Regularly reviewing and updating incident response plans to include scenarios involving network device DoS is also advisable.

Description

CVE-2026-21914 is a high-severity improper locking vulnerability in the GTP plugin of Juniper Networks Junos OS on SRX Series devices. An unauthenticated attacker can send a malformed GTP Modify Bearer Request message that causes a lock to be acquired and never released, leading to a watchdog timeout and FPC crash. This results in a denial-of-service condition causing complete traffic outage until the device recovers. The vulnerability affects multiple Junos OS versions prior to specific patched releases across versions 22.4R3-S8 through 25.2R2. Exploitation requires no authentication or user interaction and can be performed remotely over the network. There are no known exploits in the wild as of now. The CVSS v3.1 score is 7.

Impact

For European organizations, this vulnerability poses a significant risk to network availability, especially for those relying on Juniper SRX Series devices as perimeter firewalls or core network security appliances. A successful exploit can cause a complete traffic outage, disrupting business operations, critical communications, and potentially impacting services dependent on continuous network connectivity. Sectors such as telecommunications, finance, government, and critical infrastructure operators are particularly vulnerable due to their reliance on stable and secure network infrastructure. The denial-of-service condition could lead to operational downtime, financial losses, and reputational damage. Additionally, the ease of exploitation without authentication increases the threat from opportunistic attackers or automated scanning tools. Given the widespread deployment of Juniper SRX devices in Europe, the potential scale of impact is considerable, especially if attackers target multiple devices simultaneously or leverage this vulnerability as part of a larger attack campaign.

CWE-667Improper Locking (opens in a new tab)
Class weakness
The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.
Implementation · Libraries or Frameworks
Use industry standard APIs to implement locking mechanism.
Attack patterns
Leveraging Race Conditions via Symbolic Links (opens in a new tab)
Forced Deadlock (opens in a new tab)
Leveraging Race Conditions (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 22 Jan 2026, 21:39 UTC

WeaknessesCWE-667

Technical details

References

Community reviews

Related threats