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2021-10 Security Bulletin: 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. (CVE-2021-31379)



Article ID: JSA11247 SECURITY_ADVISORIES Last Updated: 13 Oct 2021Version: 1.0
Product Affected:
This issue affects Junos OS 17.2, 17.3, 17.4, 18.1, 18.2, 18.3, 18.4, 19.1, 19.2, 19.3. Affected platforms: MX Series

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


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:
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.

The following minimal configuration is necessary:

[chassis fpc <fpc-number> pic <pic-number> inline-services bandwidth <bandwidth>]
[interfaces <si-interface-name> unit <inside-logical-unit> family inet]
[interfaces <si-interface-name> unit <inside-logical-unit> family inet6]
[interfaces <si-interface-name> unit <inside-logical-unit> service-domain inside]
[interfaces <si-interface-name> unit <outside-logical-unit> family inet]
[interfaces <si-interface-name> unit <outside-logical-unit> family inet6]
[interfaces <si-interface-name> unit <outside-logical-unit> service-domain outside]
[services softwire softwire-concentrator map-e <mape-instance-name> version03]
[services softwire softwire-concentrator map-e <mape-instance-name> softwire-address <IPv6-Address>]
[services softwire softwire-concentrator map-e <mape-instance-name> ipv4-prefix <IPv4-Prefix> mape-prefix <IPv6-Prefix>]
[services softwire softwire-concentrator map-e <mape-instance-name> ea-bits-len <0..48>]
[services softwire softwire-concentrator map-e <mape-instance-name> psid-off[set <0..16>]
[services softwire softwire-concentrator map-e <mape-instance-name> psid-length <0..16>]
[services softwire softwire-concentrator map-e <mape-instance-name> mtu-ipv6 <1280..9192>]
[services softwire softwire-concentrator map-e <mape-instance-name> v4-reassembly]
[services softwire rule <mape-rule-name> match-direction input term <term-name> then map-e <mape-instance-name>]
[services service-set <service-set-name> softwire-rules <mape-rule-name>]
[services service-set <service-set-name> next-hop-service inside-service-interface <si-interface-name.inside-logical-unit> outside-service-interface <si-interface-name.outside-logical-unit>]

Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

This issue was found during internal product security testing or research.

This issue has been assigned 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.

This issue is being tracked as 1468454.


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.


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.
Software releases or updates are available for download at
Modification History:
2021-10-13: Initial Publication.
CVSS Score:
7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
Severity Level:
Severity Assessment:
Information for how Juniper Networks uses CVSS can be found at KB 16446 "Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories."

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