A Protection Mechanism Failure vulnerability in the J-Web HTTP service of Juniper Networks Junos OS allows a remote unauthenticated attacker to perform Person-in-the-Middle (PitM) attacks against the device. This issue affects: Juniper Networks Junos OS 12.3 versions prior to 12.3R12-S20; 15.1 versions prior to 15.1R7-S11; 18.3 versions prior to 18.3R3-S6; 18.4 versions prior to 18.4R3-S10; 19.1 versions prior to 19.1R3-S7; 19.2 versions prior to 19.2R3-S4; 19.3 versions prior to 19.3R3-S4; 19.4 versions prior to 19.4R3-S6; 20.1 versions prior to 20.1R3-S2; 20.2 versions prior to 20.2R3-S3; 20.3 versions prior to 20.3R3-S1; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R3; 21.2 versions prior to 21.2R2.
Published 2021-10-19 19:15:12
Updated 2021-10-25 17:17:56
View at NVD,   CVE.org

Products affected by CVE-2021-31386

Exploit prediction scoring system (EPSS) score for CVE-2021-31386

0.25%
Probability of exploitation activity in the next 30 days EPSS Score History
~ 65 %
Percentile, the proportion of vulnerabilities that are scored at or less

CVSS scores for CVE-2021-31386

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source First Seen
2.6
LOW AV:N/AC:H/Au:N/C:P/I:N/A:N
4.9
2.9
NIST
5.9
MEDIUM CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
2.2
3.6
NIST
5.3
MEDIUM CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
1.6
3.6
Juniper Networks, Inc.

CWE ids for CVE-2021-31386

  • The product does not adequately verify the identity of actors at both ends of a communication channel, or does not adequately ensure the integrity of the channel, in a way that allows the channel to be accessed or influenced by an actor that is not an endpoint.
    Assigned by: sirt@juniper.net (Secondary)
  • The product does not encrypt sensitive or critical information before storage or transmission.
    Assigned by: sirt@juniper.net (Secondary)
  • The product does not implement a required step in a cryptographic algorithm, resulting in weaker encryption than advertised by the algorithm.
    Assigned by: sirt@juniper.net (Secondary)
  • The product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product.
    Assigned by: sirt@juniper.net (Secondary)

References for CVE-2021-31386

  • https://kb.juniper.net/JSA11254
    2021-10 Security Bulletin: Junos OS: When using J-Web with HTTP an attacker may retrieve encryption keys via Person-in-the-Middle attacks. (CVE-2021-31386) - Juniper Networks
    Vendor Advisory
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