CVE-2020-15938Network attack vector

Policy bypass via non-HTTP traffic misclassification

Published Mar 4, 2021 · Updated Oct 25, 2024

Security policy bypass in Fortinet FortiOS 6.2.5 and earlier and 6.4.0 through 6.4.2 allows remote attackers to evade transparent proxy rules. On ports 80 and 443, the traffic classifier treats non-HTTP/S streams without a valid HTTP header as ineligible for redirection instead of sending them to the transparent proxy policy. The device must be configured for transparent proxying and lie on the traffic path; successful use lets disallowed non-HTTP/S traffic cross without policy processing.

CVSS severity7.5
High
EPSS probability0.75%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Security policy bypass in Fortinet FortiOS 6.2.5 and earlier and 6.4.0 through 6.4.2 allows remote attackers to evade transparent proxy rules. On ports 80 and 443, the traffic classifier treats non-HTTP/S streams without a valid HTTP header as ineligible for redirection instead of sending them to the transparent proxy policy. The device must be configured for transparent proxying and lie on the traffic path; successful use lets disallowed non-HTTP/S traffic cross without policy processing.

The record

CVE
CVE-2020-15938
Published
Mar 4, 2021
Updated
Oct 25, 2024
Vendor
Fortinet
Product
FortiOS
Classifications
T1562.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 4, 2021CVE publishedPublication date reported by the CVE source.
  2. Oct 25, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=FortiOS 6.4.2, 6.2.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Fortinet · FortiOSversion=FortiOS 6.4.2, 6.2.5

Published CVSS scores

4.3NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
4.0Fortinet PSIRTCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:N
7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

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

T1562.001Impair Defenses: Disable or Modify Tools

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

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Your stack

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