CVE-2026-21918

15.01.2026, 21:16

A Double Free vulnerability in the flow processing daemon (flowd) of Juniper Networks Junos OS on SRX and MX Series allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). On all SRX and MX Series platforms, when during TCP session establishment a specific sequence of packets is encountered a double free happens. This causes flowd to crash and the respective FPC to restart.





This issue affects Junos OS on SRX and MX Series:



  *  all versions before 22.4R3-S7,
  *  23.2 versions before 23.2R2-S3,
  *  23.4 versions before 23.4R2-S4,
  *  24.2 versions before 24.2R2.

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
NIST	NIST	7.5 HIGH	NETWORK	LOW	NONE	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
juniper	CNA	7.5 HIGH	NETWORK	LOW	NONE	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CISA-ADP	ADP	---				---

Base Score

CVSS 3.x

EPSS Score

Percentile: Unknown

Common Weakness Enumeration

CWE-415 - Double Free
The product calls free() twice on the same memory address, potentially leading to modification of unexpected memory locations.

Vulnerability Media Exposure

[GERMAN] Juniper Junos OS, Junos Space: Mehrere Schwachstellen
Ein Angreifer kann mehrere Schwachstellen in Juniper JUNOS und Juniper Junos Space ausnutzen, um falsche Informationen darzustellen, beliebigen Code mit Root-Rechten auszuführen, Daten zu manipulieren, vertrauliche Informationen offenzulegen und einen Denial-of-Service-Zustand zu verursachen.
Published: 2026-01-14T23:00:00+00:00

References

https://kb.juniper.net/JSA106018

https://supportportal.juniper.net/JSA106018