CVE-2021-31386Network attack vector

Encryption-key disclosure via unencrypted J-Web HTTP

Published Oct 19, 2021 · Updated Sep 17, 2024

Protection mechanism failure in J-Web on Juniper Networks Junos OS allows remote attackers to retrieve encryption keys over HTTP. The J-Web HTTP service transmits sensitive management traffic without transport encryption, enabling an on-path attacker to intercept the keys. The device must have system services web-management http enabled, and a user must interact with J-Web while the attacker occupies the traffic path.

CVSS severity5.3
Medium
EPSS probability0.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Protection mechanism failure in J-Web on Juniper Networks Junos OS allows remote attackers to retrieve encryption keys over HTTP. The J-Web HTTP service transmits sensitive management traffic without transport encryption, enabling an on-path attacker to intercept the keys. The device must have system services web-management http enabled, and a user must interact with J-Web while the attacker occupies the traffic path.

The record

CVE
CVE-2021-31386
Published
Oct 19, 2021
Updated
Sep 17, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-311, CWE-325, CWE-693, CWE-300, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 19, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=12.3 <12.3R12-S20
  2. Affected versionversion=15.1 <15.1R7-S11
  3. Affected versionversion=18.3 <18.3R3-S6
  4. Affected versionversion=18.4 <18.4R3-S10
  5. Affected versionversion=19.1 <19.1R3-S7
  6. Affected versionversion=19.2 <19.2R3-S4
  7. Affected versionversion=19.3 <19.3R3-S4
  8. Affected versionversion=19.4 <19.4R3-S6
  9. Affected versionversion=20.1 <20.1R3-S2
  10. Affected versionversion=20.2 <20.2R3-S3
  11. Affected versionversion=20.3 <20.3R3-S1
  12. Affected versionversion=20.4 <20.4R3
  13. Affected versionversion=21.1 <21.1R3
  14. Affected versionversion=21.2 <21.2R2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=12.3 <12.3R12-S20; version=15.1 <15.1R7-S11; version=18.3 <18.3R3-S6; version=18.4 <18.4R3-S10; version=19.1 <19.1R3-S7; version=19.2 <19.2R3-S4; version=19.3 <19.3R3-S4; version=19.4 <19.4R3-S6; version=20.1 <20.1R3-S2; version=20.2 <20.2R3-S3; version=20.3 <20.3R3-S1; version=20.4 <20.4R3; version=21.1 <21.1R3; version=21.2 <21.2R2

Published CVSS scores

5.9NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
2.6NIST NVDAV:N/AC:H/Au:N/C:P/I:N/A:N
5.3Juniper NetworksCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-311Missing Encryption of Sensitive Data
CWE-325Missing Cryptographic Step
CWE-693Protection Mechanism Failure
CWE-300Channel Accessible by Non-Endpoint
T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo