CVE-2021-31379

Public Exploit
Junos OS: MX Series: MPC 7/8/9/10/11 cards with MAP-E: PFE halts when an attacker sends malformed IPv4 or IPv6 traffic inside the MAP-E tunnel.

Description

An Incorrect Behavior Order vulnerability in the MAP-E automatic tunneling mechanism of Juniper Networks Junos OS allows an attacker to send certain malformed IPv4 or IPv6 packets to cause a Denial of Service (DoS) to the PFE on the device which is disabled as a result of the processing of these packets. Continued receipt and processing of these malformed IPv4 or IPv6 packets will create a sustained Denial of Service (DoS) condition. This issue only affects MPC 7/8/9/10/11 cards, when MAP-E IP reassembly is enabled on these cards. An indicator of compromise is the output: FPC ["FPC ID" # e.g. "0"] PFE #{PFE ID # e.g. "1"] : Fabric Disabled Example: FPC 0 PFE #1 : Fabric Disabled when using the command: show chassis fabric fpcs An example of a healthy result of the command use would be: user@device-re1> show chassis fabric fpcs Fabric management FPC state: FPC 0 PFE #0 Plane 0: Plane enabled Plane 1: Plane enabled Plane 2: Plane enabled Plane 3: Plane enabled Plane 4: Plane enabled Plane 5: Plane enabled Plane 6: Plane enabled Plane 7: Plane enabled This issue affects: Juniper Networks Junos OS on MX Series with MPC 7/8/9/10/11 cards, when MAP-E IP reassembly is enabled on these cards. 17.2 version 17.2R1 and later versions; 17.3 versions prior to 17.3R3-S9; 17.4 versions prior to 17.4R2-S12, 17.4R3-S3; 18.1 versions prior to 18.1R3-S11; 18.2 versions prior to 18.2R2-S6, 18.2R3-S3; 18.3 versions prior to 18.3R2-S4, 18.3R3-S1; 18.4 versions prior to 18.4R1-S8, 18.4R2-S5, 18.4R3; 19.1 versions prior to 19.1R1-S6, 19.1R2-S2, 19.1R3; 19.2 versions prior to 19.2R1-S5, 19.2R2; 19.3 versions prior to 19.3R2-S5, 19.3R3. This issue does not affect Juniper Networks Junos OS versions prior to 17.2R1.

Remediation

Solution:

  • The following software releases have been updated to resolve this specific issue: 17.3R3-S9, 17.4R2-S12, 17.4R3-S3, 18.1R3-S11, 18.2R2-S6, 18.2R3-S3, 18.3R2-S4, 18.3R3-S1, 18.4R1-S8, 18.4R2-S5, 18.4R3, 19.1R1-S6, 19.1R2-S2, 19.1R3, 19.2R1-S5, 19.2R2, 19.3R2-S5, 19.3R3, 19.4R1, and all subsequent releases.

Workaround:

  • To work around this issue customers can either: 1. Disable Mapping of Address and port - Encapsulation (MAP-E) as an inline service on MX Series routers that use MPC and MIC interfaces. or 2. Determine where the MAP-E v4 or v6 reassembly exists, review the following hierarchies and disable the "v4-reassembly;" and "v6-reassembly;" options where they exist: [services softwire softwire-concentrator] [services softwires softwire-types] [security softwires] and the following syntaxes: map-e name { v4-reassembly; <<<<< DISABLE the v4-reassembly option. v6-reassembly; <<<<< DISABLE the v6-reassembly option. }

Category

7.5
CVSS
Severity: High
CVSS 3.1 •
CVSS 2.0 •
EPSS 0.34%
Vendor Advisory juniper.net Vendor Advisory juniper.net
Affected: Juniper Networks Junos OS
Published at:
Updated at:

References

Link Tags
https://kb.juniper.net/JSA11247 exploit mitigation vendor advisory
https://www.juniper.net/documentation/en_US/junos/topics/topic-map/map-e-configuring.html vendor advisory

Frequently Asked Questions

What is the severity of CVE-2021-31379?
CVE-2021-31379 has been scored as a high severity vulnerability.
How to fix CVE-2021-31379?
To fix CVE-2021-31379: The following software releases have been updated to resolve this specific issue: 17.3R3-S9, 17.4R2-S12, 17.4R3-S3, 18.1R3-S11, 18.2R2-S6, 18.2R3-S3, 18.3R2-S4, 18.3R3-S1, 18.4R1-S8, 18.4R2-S5, 18.4R3, 19.1R1-S6, 19.1R2-S2, 19.1R3, 19.2R1-S5, 19.2R2, 19.3R2-S5, 19.3R3, 19.4R1, and all subsequent releases.
Is CVE-2021-31379 being actively exploited in the wild?
It is possible that CVE-2021-31379 is being exploited or will be exploited in a near future based on public information. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2021-31379?
CVE-2021-31379 affects Juniper Networks Junos OS.
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