CVE-2026-33800
MEDIUMDescription
An Unchecked Input for Loop Condition vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS on MX Series allows an unauthenticated, adjacent attacker to cause a Denial-of-Service (DoS).Micro-BFD session flaps generate respective up/down events which are queued by PFEMAN for processing. Especially in a Virtual-Chassis (VC) scenario with locality‑bias configured, processing takes a significant amount of time for each event. If these sessions keep flapping, new events are constantly added, and in turn PFEMAN never completes processing these events. This results in the PFEMAN watchdog timer expiring, which causes the FPC to crash and restart, representing a complete service outage. This issue only affects MX series FPCs up to and including MPC9, and LC2101/2103 and LC480. It does not affect MPC10/11, LC4800/9600, and MX304. This issue affects Junos OS on MX Series: * all versions before 23.2R2-S7, * 23.4 versions before 23.4R2-S8, * 24.2 versions before 24.2R2-S4, * 24.4 versions before 24.4R2-S3, * 25.2 versions before 25.2R2.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Exploit Intelligence
Low risk: more likely to be exploited than 6% of all known CVEs.
References
Related Vulnerabilities
Other CWE-606 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2023-3446 | Medium | 5.3 | 6.5% | - | Fix |
| CVE-2023-5678 | Medium | 5.3 | 4.5% | - | Fix |
| CVE-2023-3817 | Medium | 5.3 | 3.0% | - | Fix |
| CVE-2024-43499 | High | 7.5 | 2.6% | - | Fix |
| CVE-2023-6237 | Medium | 5.9 | 2.3% | - | Fix |
| CVE-2026-1519 | High | 7.5 | 1.6% | - | Fix |
Common questions
How do I fix CVE-2026-33800?
No published fix for CVE-2026-33800 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-33800 being actively exploited?
Not that we know of. CVE-2026-33800 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.17% is the estimated probability that it will be exploited in the next 30 days. That is higher than 6% of all scored CVEs.
How severe is CVE-2026-33800?
CVE-2026-33800 has a CVSS v3 base score of 6.5, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-20.