CVE-2026-33800
Junos OS: MX Series: In a VC scenario a high rate of micro-BFD session flaps will cause an FPC crash
Description
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. 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.
INFO
Published Date :
July 9, 2026, 9:16 p.m.
Last Modified :
July 9, 2026, 9:16 p.m.
Remotely Exploit :
No
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-33800
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | 8cbe9d5a-a066-4c94-8978-4b15efeae968 | ||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 4.0 | HIGH | 8cbe9d5a-a066-4c94-8978-4b15efeae968 | ||||
| CVSS 4.0 | HIGH | [email protected] |
Solution
- Update Junos OS to version 23.2R2-S7 or later.
- Update Junos OS to version 23.4R2-S8 or later.
- Update Junos OS to version 24.2R2-S4 or later.
- Update Junos OS to version 24.4R2-S3 or later.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-33800.
| URL | Resource |
|---|---|
| https://supportportal.juniper.net/JSA110075 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-33800 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-33800
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-33800 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-33800 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Jul. 09, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'Juniper Networks', 'product': 'Junos OS', 'versions': [{'status': 'affected', 'version': '0', 'lessThan': '23.2R2-S7', 'versionType': 'custom'}, {'status': 'affected', 'version': '23.4', 'lessThan': '23.4R2-S8', 'versionType': 'custom'}, {'status': 'affected', 'version': '24.2', 'lessThan': '24.2R2-S4', 'versionType': 'custom'}, {'status': 'affected', 'version': '24.4', 'lessThan': '24.4R2-S3', 'versionType': 'custom'}, {'status': 'affected', 'version': '25.2', 'lessThan': '25.2R2', 'versionType': 'custom'}], 'platforms': ['MX Series'], 'defaultStatus': 'unaffected'}] Added Description 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. 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. Added CVSS V4.0 AV:A/AC:L/AT:N/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 Added CVSS V3.1 AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-606 Added Reference https://supportportal.juniper.net/JSA110075