Junos OS: Specific unknown traffic pattern causes FPC and system to crash when packet capturing is enabled

published 2025-07-11 15 mo ago modified 2026-06-17 4 mo ago also EUVD-2025-21153

cvss: 5.9; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 42%
public exploits: 0; none known

An Improper Handling of Exceptional Conditions vulnerability in Berkeley Packet Filter (BPF) processing of Juniper Networks Junos OS allows an attacker, in rare cases, sending specific, unknown traffic patterns to cause the FPC and system to crash and restart.

BPF provides a raw interface to data link layers in a protocol independent fashion. Internally within the Junos kernel, due to a rare timing issue (race condition), when a BPF instance is cloned, the newly created interface causes an internal structure leakage, leading to a system crash. The precise content and timing of the traffic patterns is indeterminate, but has been seen in a lab environment multiple times.

This issue is more likely to occur when packet capturing is enabled. See required configuration below.

This issue affects Junos OS:

* all versions before 21.2R3-S9, * from 21.4 before 21.4R3-S10, * from 22.2 before 22.2R3-S6, * from 22.4 before 22.4R3-S7, * from 23.2 before 23.2R2-S3, * from 23.4 before 23.4R2-S3, * from 24.2 before 24.2R1-S1, 24.2R2.

Patch / fix

fixed in 1

Juniper Networks Junos OS 21.2R3-S9, 21.4R3-S10, 22.2R3-S6, 22.4R3-S7, 23.2R2-S3, 23.4R2-S3, 24.2R1-S1, 24.2R2

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 15 mo ago (2025-07-11)

Exploit prediction

0.50% chance of exploitation in the next 30 days, higher than 42% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	5.9	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA	4.0	8.2	CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:Y/R:A/RE:M
CNA	4.0	8.2	CVSS:4.0/AV:N/AC:L/AT:P/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

Affected products

Juniper Networks Junos OS

Classification

Weakness

CWE-755 Improper Handling of Exceptional Conditions

References

supportportal.juniper.net /JSA100052
vendor-advisory
juniper.net /documentation/us/en/software/junos/network-mgmt/topics/topic-map/analyze-network-traffic-by-using-packet-capt
technical-description

Sources

CVE List CVE-2025-52948
NVD CVE-2025-52948

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary