CVE-2020-5233Network attack vector

Authentication token theft via unsafe redirect validation

Published Jan 30, 2020 · Updated Aug 4, 2024

OAuth2 Proxy before 5.0 allows remote attackers to harvest authentication tokens via an open redirect during sign-in. The IsValidRedirect function accepts redirect paths beginning /, which browsers interpret as a cross-domain destination, bypassing the intended same-site restriction. Exploitation requires a victim to follow the crafted authentication link; impact is token disclosure and redirection, not service interruption.

CVSS severity6.1
Medium
EPSS probability1.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OAuth2 Proxy before 5.0 allows remote attackers to harvest authentication tokens via an open redirect during sign-in. The IsValidRedirect function accepts redirect paths beginning /, which browsers interpret as a cross-domain destination, bypassing the intended same-site restriction. Exploitation requires a victim to follow the crafted authentication link; impact is token disclosure and redirection, not service interruption.

The record

CVE
CVE-2020-5233
Published
Jan 30, 2020
Updated
Aug 4, 2024
Vendor
OAuth2 Proxy
Product
OAuth2 Proxy
Classifications
CWE-601
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 30, 2020CVE 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=< 5.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OAuth2 Proxy · OAuth2 Proxyversion=< 5.0.0

Published CVSS scores

5.9GitHub CNACVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:H/A:L
5.8NVDAV:N/AC:M/Au:N/C:P/I:P/A:N
6.1NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/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.

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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-601URL Redirection to Untrusted Site ('Open Redirect')

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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