Vulnerability report

Active exploitation observed Confirmed confidence Not in CISA KEV

CVE-2020-11991

Cocoon

Apache / Cocoon · Apache Cocoon 2.1.0 to 2.1.12

Watch CVE-2020-11991 Browse KEV feed
Severity
CVSS 7.5 · High
Confidence
Confirmed
Exploit status
Observed in sensors
EPSS
72.5%
First observed
27 Jun 2026
Last observed
04 Oct 2026

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2020-11991 is an unauthenticated vulnerability affecting Apache Cocoon. When using the StreamGenerator, the code parse a user-provided XML. A specially crafted XML, including external system entities, could be...

Is it exploited?

Yes. Previdian sensors observed exploitation attempts with confirmed confidence. Also confirmed by third-party sources.

Who is affected?

Apache / Cocoon apache cocoon 2.1.0 to 2.1.12.

What should we do?

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

Overview

When using the StreamGenerator, the code parse a user-provided XML

When using the StreamGenerator, the code parse a user-provided XML. A specially crafted XML, including external system entities, could be used to access any file on the server system.

n/a Affected
Apache Cocoon
Apache Cocoon 2.1.0 to 2.1.12
Published
11 Sep 2020
Exploitation Reported
29 Jul 2025
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

nuclei_scanner apache

CVE References

  • CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2020-11991
  • Apache Mailing List lists.apache.org · CVE Record https://lists.apache.org/thread.html/r77add973ea521185e1a90aca00ba9da...

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 29 Jul 2025

A trusted third party reported exploitation.

Active exploitation observed

Previdian sensor

First observed 27 Jun 2026

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

Proof of concept available

Nuclei Templates

Recorded 12 Jun 2026

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
The Shadowserver First 2025-07-29 00:00 UTC
Previdian Sensors 2026-07-23 11:17 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.

15

Attempts observed

10

Unique attacker IPs

8

Attacker countries

BG · CH · FI · FR · NL · SC · US · YE

10

Sensors observed

CVE-2020-11991 exploitation attempts over the last 84 days

Daily events observed by Previdian sensors

Updated 09 Oct 2026

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0
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18 Jul 4 Aug 21 Aug 7 Sep 9 Oct

First observed 27 Jun 2026 · Last observed 04 Oct 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
11
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/2020/CVE-2020-11991.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

7.5 High

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

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

EPSS

72.5%

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

Weaknesses

Improper Restriction of XML External Entity Reference CWE-611

All CVSS Scores

CVSS v3.1 7.5 High

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

CVSS v2.0 5.0 Medium

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

Potential Proof of Concepts

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

Apache Cocoon 2.1.12 - XML Injection

nuclei · Created Unknown

Timeline

From disclosure to observed exploitation

  1. 13:00 UTC

    Virtual patch available

    Compensating WAF rule available to block exploitation

  2. 09:39 UTC

    Indicators of compromise added (30)

    Indicators of compromise recorded

  3. 09:39 UTC

    Observed by Previdian sensors

    Evidence-backed exploitation signal

  4. 14:20 UTC

    Public PoC available

    Public proof-of-concept code published

  5. 00:00 UTC

    Added to Previdian KEV Feed

    High-confidence, third-party attested exploitation

  6. 00:00 UTC

    Nuclei template available

    Scanner coverage available

  7. 13:28 UTC

    CVE published

    Vulnerability disclosed publicly

  8. 00:00 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-2020-11991

Free JSON includes basic KEV fields 
{
  "cve_id": "CVE-2020-11991",
  "confidence": "Confirmed",
  "cvss_score": 7.5,
  "cvss_estimated": false,
  "epss_score": 0.72456,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": true
  },
  "sensor_telemetry": { "attempts": 15, "sensors": 10 }
}