Vulnerability report

Active exploitation observed Confirmed confidence Not in CISA KEV

CVE-2021-31805

Apache Struts Remote Code Execution

Apache / Apache Struts · 2.0.0 to 2.5.29

View live feed Monitor via API Watch CVE-2021-31805
Severity
CVSS 9.8 · Critical
Confidence
Confirmed
Exploit status
Observed in sensors
EPSS
85.4%
First observed
12 Jun 2026
Last observed
09 Sep 2026

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2021-31805 is an unauthenticated vulnerability affecting Apache Apache Struts. The fix issued for CVE-2020-17530 was incomplete. So from Apache Struts 2.0.0 to 2.5.29, still some of the tag’s attributes could...

Is it exploited?

Yes. Previdian sensors observed exploitation attempts with confirmed confidence.

Who is affected?

Apache / Apache Struts 2.0.0 to 2.5.29.

What should we do?

Patch immediately, validate internet-facing exposure, and monitor for matching requests.

Overview

The fix issued for CVE-2020-17530 was incomplete

The fix issued for CVE-2020-17530 was incomplete. So from Apache Struts 2.0.0 to 2.5.29, still some of the tag’s attributes could perform a double evaluation if a developer applied forced OGNL evaluation by using the %{...} syntax.

Using forced OGNL evaluation on untrusted user input can lead to a Remote Code Execution and security degradation.

Vendor Product Affected Status
Apache Software Foundation Apache Struts 2.0.0 to 2.5.29 Affected
Published
12 Apr 2022
Exploitation Reported
12 Jun 2026
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

apache nuclei_scanner

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

Previdian

Recorded 12 Jun 2026

Previdian independently recorded this as exploited after first seeing it in honeypot sensors.

Active exploitation observed

Previdian sensor

First observed 12 Jun 2026

Previdian first observed exploitation attempts targeting this vulnerability in our honeypot sensors.

Proof of concept available

GitHub

Recorded 15 Apr 2022

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

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

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Source Added
Previdian First 2026-06-12 00:32 UTC

Operational indicators for this CVE are listed under Detection.

Sensor telemetry

First-party evidence of exploitation activity

Previdian sensors recorded exploitation attempts targeting this vulnerability. The cards and chart show volume, unique attackers, and daily activity.

4

Attempts observed

4

Unique attacker IPs

3

Attacker countries

FI · FR · US

4

Sensors observed

CVE-2021-31805 exploitation attempts over the last 91 days

Daily events observed by Previdian sensors

Updated 13 Sep 2026

1
0
0
0
0
0
1
0
0
0
0
0
1
0
9
5
1
0
20
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
1
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
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0
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1
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1
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0
0
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0
0
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1
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0
0
15 Jun 4 Jul 23 Jul 11 Aug 13 Sep

First observed 12 Jun 2026 · Last observed 09 Sep 2026

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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
1
4
0

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

Virtual patch status

Previdian virtual patch guidance is available for this CVE.

AWS WAF Cloudflare ModSecurity

Attacker IP Indicators

Attacker IP indicators observed · available in Pro and Enterprise.

Sensor-derived attacker IP indicators are available to Pro and Enterprise accounts under Detection and through the Pro API.

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Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner Reference Detected
Nuclei https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-31805.yaml 25 Apr 2025

Virtual Patch Detail

Compensating WAF rules for this CVE.

Available

Enterprise feature. Virtual patch rule content and deployable vendor exports (ModSecurity, Cloudflare, AWS WAF) are available to Previdian Enterprise users.

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Risk and context

Severity, weaknesses, and research context

CVSS v3.1

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

EPSS

85.4%

Weaknesses

Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection') CWE-917

All CVSS Scores

CVSS v3.1 9.8 Critical

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

CVSS v2.0 7.5 High

AV:N/AC:L/Au:N/C:P/I:P/A:P

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

Wrin9/CVE-2021-31805

github · Created 2022-04-15 04:23:44 UTC · 35 stars · AI assessment 90%

S2-062 (CVE-2021-31805) / S2-061 / S2-059 RCE

Apache Struts2 S2-062 - Remote Code Execution

nuclei · Created Unknown

Timeline

From disclosure to observed exploitation

  1. Virtual patch available

    Compensating WAF rule available to block exploitation

  2. Indicators of compromise added (25)

    Indicators of compromise recorded

  3. Observed by Previdian sensors

    Evidence-backed exploitation signal

  4. Nuclei template available

    Scanner coverage available

  5. Public PoC available

    Public proof-of-concept code published

  6. CVE published

    Vulnerability disclosed publicly

  7. 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-2021-31805

Free JSON includes basic KEV fields 
{
  "cve_id": "CVE-2021-31805",
  "confidence": "Confirmed",
  "cvss_score": 9.8,
  "cvss_estimated": false,
  "epss_score": 0.85433,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": true
  },
  "sensor_telemetry": { "attempts": 4, "sensors": 4 }
}