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Fencer Vulns
high 7.5

CVE-2023-36841 json

Junos OS: MX Series: Receipt of malformed TCP traffic will cause a Denial of Service

published 2023-10-12 3 y ago modified 2026-06-17 4 mo ago also EUVD-2023-40761

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 49%
public exploits
0
none known

Summary

An Improper Check for Unusual or Exceptional Conditions vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS on MX Series allows a unauthenticated network-based attacker to cause an infinite loop, resulting in a Denial of Service (DoS).

An attacker who sends malformed TCP traffic via an interface configured with PPPoE, causes an infinite loop on the respective PFE. This results in consuming all resources and a manual restart is needed to recover.

This issue affects interfaces with PPPoE configured and tcp-mss enabled.

This issue affects Juniper Networks Junos OS

* All versions prior to 20.4R3-S7; * 21.1 version 21.1R1 and later versions; * 21.2 versions prior to 21.2R3-S6; * 21.3 versions prior to 21.3R3-S5; * 21.4 versions prior to 21.4R3-S3; * 22.1 versions prior to 22.1R3-S4; * 22.2 versions prior to 22.2R3; * 22.3 versions prior to 22.3R2-S2; * 22.4 versions prior to 22.4R2;

Patch / fix

  • Juniper Networks Junos OS 20.4R3-S7, 21.2R3-S6, 21.3R3-S5, 21.4R3-S3, 22.1R3-S4, 22.2R3, 22.3R2-S2, 22.3R3, 22.4R2
  • juniper_networks junos_os 20.4r3-s7, 21.1, 21.2r3-s6, 21.3r3-s5, 21.4r3-s3, 22.1r3-s4, 22.2r3, 22.3r2-s2, 22.3r3, 22.4r2

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
2 y ago

Exploit prediction

0.62% chance of exploitation in the next 30 days, higher than 49% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Juniper Networks Junos OS
  • juniper_networks junos_os

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.