Vulnerability report

Exploited in the wild High confidence Not in CISA KEV

CVE-2024-21620

Junos OS Cross-Site Scripting

Juniper Networks / Junos OS · affected before 20.4R3-S10

Watch CVE-2024-21620 Browse KEV feed
Severity
CVSS 8.8 · High
Confidence
High
Exploit status
Exploited in the wild
EPSS
0.9%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2024-21620 is an unauthenticated vulnerability affecting Juniper Networks Junos OS. An Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in J-Web of Juniper...

Is it exploited?

Yes. Previdian tracks this CVE as a known exploited vulnerability. Confidence is high. Also confirmed by third-party sources.

Who is affected?

Juniper Networks / Junos OS affected before 20.4r3-s10.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

Junos OS Cross-Site Scripting

An Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in J-Web of Juniper Networks Junos OS on SRX Series and EX Series allows an attacker to construct a URL that when visited by another user enables the attacker to execute commands with the target's permissions, including an administrator.

A specific invocation of the emit_debug_note method in webauth_operation.php will echo back the data it receives.

This issue affects Juniper Networks Junos OS on SRX Series and EX Series: * All versions earlier than 20.4R3-S10; * 21.2 versions earlier than 21.2R3-S8; * 21.4 versions earlier than 21.4R3-S6; * 22.1 versions earlier than 22.1R3-S5; * 22.2 versions earlier than 22.2R3-S3; * 22.3 versions earlier than 22.3R3-S2; * 22.4 versions earlier than 22.4R3-S1; * 23.2 versions earlier than 23.2R2; * 23.4 versions earlier than 23.4R2.

Juniper Networks Affected
Junos OS
Before 20.4R3-S10 Before 21.2R3-S8 Before 21.4R3-S6 Before 22.1R3-S5 Before 22.2R3-S3 Before 22.3R3-S2 Before 22.4R3-S1 Before 23.2R2 Before 23.4R2
View vendor advisory (opens in new tab)
Published
25 Jan 2024
Exploitation Reported
07 Mar 2026
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
Required

CVE References

Exploitation evidence

Why Previdian marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

The Shadowserver

Recorded 07 Mar 2026

A trusted third party reported exploitation.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

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Source Added
The Shadowserver First 2026-03-07 00:00 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
0
0
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Scanner coverage

No scanner integrations recorded yet.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

No detection artifacts or sensor request patterns are available for this CVE yet.

Check back as sensor telemetry and scanner integrations are updated.

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

8.8 High

Potential damage if exploited. Separate from whether attackers are using it.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS

0.9%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') CWE-79

Timeline

From disclosure to observed exploitation

  1. 00:00 UTC

    Added to Previdian KEV Feed

    High-confidence, third-party attested exploitation

  2. 22:50 UTC

    CVE published

    Vulnerability disclosed publicly

  3. 19:38 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2024-21620

Sample API response 
{
  "cve_id": "CVE-2024-21620",
  "confidence": "High",
  "cvss_score": 8.8,
  "cvss_estimated": false,
  "epss_score": 0.00908,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}