CVSS: v3.1: 5.3 (CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H)CVSS: v4.0: 6.0 (CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:Y/RE:M)
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:
To be exposed to this issue at least one sflow collector needs to be configured via:[ protocols sflow collector <address> ]
Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
This issue was seen during production usage.
This issue has been assigned CVE-2026-57029.
The following software releases have been updated to resolve this specific issue: Junos OS Evolved: 23.4R2-S7-EVO, 24.2R2-S5-EVO, 24.4R2-S3-EVO, 25.2R2-EVO, 25.4R1-EVO, and all subsequent releases.
This issue is being tracked as 1909536 which is visible on the Customer Support website.
Note: Juniper SIRT's policy is not to evaluate releases which are beyond End of Engineering (EOE) or End of Life (EOL).
There are no known workarounds for this issue.
2026-07-08: Initial Publication