CVE-2021-42124Network attack vector

Unauthenticated session takeover via JNLP handling

Published Dec 7, 2021 · Updated Aug 4, 2024

Improper access control in Ivanti Avalanche before 6.3.3 allows remote attackers to take over sessions through the Inforail Service. JNLP file handling fails to enforce access control before granting access to an existing session. No authentication is required, but the Inforail Service must be network-reachable; successful exploitation assumes another user's session.

CVSS severity8.8
High
EPSS probability2.60%
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

Improper access control in Ivanti Avalanche before 6.3.3 allows remote attackers to take over sessions through the Inforail Service. JNLP file handling fails to enforce access control before granting access to an existing session. No authentication is required, but the Inforail Service must be network-reachable; successful exploitation assumes another user's session.

The record

CVE
CVE-2021-42124
Published
Dec 7, 2021
Updated
Aug 4, 2024
Vendor
Ivanti
Product
Avalanche
Classifications
CWE-284, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 7, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=6.3.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Ivanti · Avalancheversion=6.3.3

Published CVSS scores

8.1Trend Micro Zero Day InitiativeCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
6.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:P

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-284Improper Access Control
T1190Exploit Public-Facing Application

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