What is CVE-2026-21905?

CVE-2026-21905 is a high-severity vulnerability in Juniper Junos, classified under Loop with Unreachable Exit Condition (Infinite Loop). CVSS score: 7.5/10. Published 2026-01-15.

How severe is CVE-2026-21905?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Juniper Junos

CVE-2026-21905

A Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in the SIP application layer gateway (ALG) of Juniper Networks Junos OS on SRX Series and MX Series with MX-SPC3 or MS-MPC allows an unauthenticated network-based attac…

EPSS: 0.004 (28.3th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Juniper Junos — versions 21.2, 21.4, 22.4
Juniper Mx10004
Juniper Mx10008
Juniper Mx2008
Juniper Mx2010
Juniper Mx2020
Juniper Mx204
Juniper Mx240
Juniper Mx304
Juniper Mx480

Weakness classification (CWE)

CWE-835 — Loop with Unreachable Exit Condition (Infinite Loop)

References

sirt@juniper.net (vendor-advisory, Vendor Advisory)
sirt@juniper.net (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-21905?: CVE-2026-21905 is a high-severity vulnerability in Juniper Junos, classified under Loop with Unreachable Exit Condition (Infinite Loop). CVSS score: 7.5/10. Published 2026-01-15.
How severe is CVE-2026-21905?: High severity. CVSS v3 base score is 7.5 out of 10.