Cyber Resilience

CVE-2026-21914

Juniper Junos ≤ 22.4

Published
15 January 2026
Modified
23 January 2026
Patch / advisory
View advisory
CVSS Score v4 8.7
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:A/V:X/RE:M/U:X
EPSS Score 0.0030 22th percentile
Risk Priority 43 floored blend · peak EPSS

Summary

CVE-2026-21914 is a high-severity Improper Locking (CWE-667) vulnerability in Juniper Junos. Its CVSS base score is 8.7 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Endpoint Denial of Service (T1499); ranked at the 22th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2026-21914 is an Improper Locking vulnerability (CWE-667) in the GTP plugin of Juniper Networks Junos OS on SRX Series devices. It affects all versions prior to 22.4R3-S8, 23.2 versions before 23.2R2-S5, 23.4 versions before 23.4R2-S6, 24.2 versions before 24.2R2-S3, 24.4 versions before 24.4R2-S2, and 25.2 versions before 25.2R1-S1 or 25.2R2. The vulnerability has a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and was published on 2026-01-15.

An unauthenticated, network-based attacker can exploit this vulnerability by sending a specifically malformed GPRS Tunnelling Protocol (GTP) Modify Bearer Request message to an SRX Series device. This causes a lock to be acquired and never released in the GTP plugin, preventing other threads from acquiring the lock, which triggers a watchdog timeout. The result is an FPC crash and restart, leading to a complete traffic outage until the device automatically recovers, effectively causing a Denial-of-Service (DoS).

Juniper's security advisory JSA106015, available at kb.juniper.net/JSA106015 and supportportal.juniper.net/JSA106015, details the issue and confirms that it is resolved in the listed patched versions of Junos OS on SRX Series devices. Security practitioners should upgrade affected systems to these versions to mitigate the vulnerability.

EU & UK References

Vulnerability Data

An Improper Locking vulnerability in the GTP plugin of Juniper Networks Junos OS on SRX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (Dos). If an SRX Series device receives a specifically malformed GPRS Tunnelling Protocol (GTP) Modify…

more

Bearer Request message, a lock is acquired and never released. This results in other threads not being able to acquire a lock themselves, causing a watchdog timeout leading to FPC crash and restart. This issue leads to a complete traffic outage until the device has automatically recovered. This issue affects Junos OS on SRX Series: * all versions before 22.4R3-S8, * 23.2 versions before 23.2R2-S5, * 23.4 versions before 23.4R2-S6, * 24.2 versions before 24.2R2-S3, * 24.4 versions before 24.4R2-S2, * 25.2 versions before 25.2R1-S1, 25.2R2.

CWE(s)
CWE-667

Related Threats

MITRE ATT&CK Enterprise Techniques

T1499 Endpoint Denial of Service Impact
Adversaries may perform Endpoint Denial of Service (DoS) attacks to degrade or block the availability of services to users.
attack.mitre.org →
T1499.004 Application or System Exploitation Impact
Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.
attack.mitre.org →
T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1548 Abuse Elevation Control Mechanism Privilege Escalation
Adversaries may circumvent mechanisms designed to control privilege elevation to gain higher-level permissions.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

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CVE-2025-6549Same product: Juniper Junos
CVE-2026-21906Same product: Juniper Junos
CVE-2025-30659Same product: Juniper Junos
CVE-2026-21920Same product: Juniper Junos
CVE-2024-21586Same product: Juniper Junos
CVE-2026-57030Same product: Juniper Junos

Affected Assets

juniper
junos
22.4, 23.2, 23.4, 24.2, 24.4 · ≤ 22.4

Mitigating Controls

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly include code reviews, static analysis, and concurrency standards that prevent improper locking.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can detect race conditions and locking errors before release.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle includes concurrency and locking requirements that reduce improper locking defects.

A.8.26 Application security requirements partial match
prevents

Application security requirements can mandate proper lock acquisition/release patterns.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles address thread-safety and resource synchronization.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly prohibit missing or incorrect lock usage.

A.8.32 Change management partial match
prevents

Change management may catch locking issues introduced by modifications but does not prevent the weakness itself.

References