CVE-2020-1755Network attack vector

Unauthenticated IP-check bypass via trusted proxy header

Published Aug 16, 2022 · Updated Aug 4, 2024

Insufficient IP validation in Moodle LMS 3.8.1 and earlier allows remote attackers to bypass remote address checks via X-Forwarded-For. The getremoteaddr() function treated a client-supplied address in the proxy chain as the user's address without excluding trusted intermediary proxies. The flaw is reachable when a site trusts that header, allowing address-based restrictions and IP logging to use a forged client address.

CVSS severity5.3
Medium
EPSS probability0.54%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insufficient IP validation in Moodle LMS 3.8.1 and earlier allows remote attackers to bypass remote address checks via X-Forwarded-For. The getremoteaddr() function treated a client-supplied address in the proxy chain as the user's address without excluding trusted intermediary proxies. The flaw is reachable when a site trusts that header, allowing address-based restrictions and IP logging to use a forged client address.

The record

CVE
CVE-2020-1755
Published
Aug 16, 2022
Updated
Aug 4, 2024
Vendor
Moodle
Product
Moodle LMS
Classifications
CWE-345
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 16, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=3.8 to 3.8.1, 3.7 to 3.7.4, 3.6 to 3.6.8, 3.5 to 3.5.10 and earlier unsupported versions

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Moodle · Moodle LMSversion=3.8 to 3.8.1, 3.7 to 3.7.4, 3.6 to 3.6.8, 3.5 to 3.5.10 and earlier unsupported versions

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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

CWE-345Insufficient Verification of Data Authenticity

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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