Vulnerability report

Active exploitation observed Confirmed confidence Not in CISA KEV

CVE-2026-86538

knowns Before 0.30.0 Path Traversal

Knowns-dev / knowns · affected before 0.30.0

Watch CVE-2026-86538 Browse KEV feed
Severity
CVSS 8.7 · High
Confidence
Confirmed
Exploit status
Observed in sensors
EPSS
1.0%
First observed
14 Sep 2026
Last observed
06 Oct 2026

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2026-86538 is an unauthenticated vulnerability affecting Knowns-dev knowns. knowns versions before 0.30.0 contain a path traversal vulnerability in the POST /api/templates/preview endpoint that allows...

Is it exploited?

Yes. Previdian sensors observed exploitation attempts with confirmed confidence.

Who is affected?

Knowns-dev / knowns affected before 0.30.0.

What should we do?

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

Overview

knowns Before 0.30.0 Path Traversal

knowns versions before 0.30.0 contain a path traversal vulnerability in the POST /api/templates/preview endpoint that allows unauthenticated attackers to read arbitrary files.

Attackers can supply directory traversal sequences in the templateFile parameter to bypass path restrictions and read sensitive files like credentials and configuration through the JSON response.

knowns-dev Affected
knowns
Before 0.30.0
knowns-dev Unaffected
knowns
0.30.0
View vendor advisory (opens in new tab)
Published
07 Sep 2026
Exploitation Reported
14 Sep 2026
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

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 14 Sep 2026

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

Active exploitation observed

Previdian sensor

First observed 14 Sep 2026

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

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 Sensors First 2026-09-17 16:27 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.

626

Attempts observed

264

Unique attacker IPs

13

Attacker countries

AR · BE · BR · CA · DE · FR · HK · IN · JP · NL · SG · TW · US

17

Sensors observed

CVE-2026-86538 exploitation attempts over the last 25 days

Daily events observed by Previdian sensors

Updated 07 Oct 2026

0
2
2
2
220
70
72
8
42
14
26
46
44
4
12
0
18
4
16
10
8
0
2
4
0
13 Sep 18 Sep 23 Sep 28 Sep 7 Oct

First observed 14 Sep 2026 · Last observed 06 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
35
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

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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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 v4.0

8.7 High

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

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

EPSS

1.0%

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

Weaknesses

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') CWE-22

All CVSS Scores

CVSS v4.0 8.7 High

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

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

Timeline

From disclosure to observed exploitation

  1. 13:37 UTC

    Virtual patch available

    Compensating WAF rule available to block exploitation

  2. 16:27 UTC

    Indicators of compromise added (264)

    Indicators of compromise recorded

  3. 16:27 UTC

    Observed by Previdian sensors

    Evidence-backed exploitation signal

  4. 23:03 UTC

    CVE published

    Vulnerability disclosed publicly

  5. 22:18 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-2026-86538

Free JSON includes basic KEV fields 
{
  "cve_id": "CVE-2026-86538",
  "confidence": "Confirmed",
  "cvss_score": 8.7,
  "cvss_estimated": false,
  "epss_score": 0.00984,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": true
  },
  "sensor_telemetry": { "attempts": 626, "sensors": 17 }
}