CVE-2021-27582Public exploitNetwork attack vector

OAuth token theft via redirect URI autobinding

Published Feb 23, 2021 · Updated Aug 3, 2024

Mass assignment in MITREid Connect 1.3.3 and earlier allows remote attackers to steal OAuth tokens via crafted confirmation links. The /oauth/confirm_access handler binds HTTP query fields into the session-backed authorizationRequest, so an attacker-supplied redirectUri replaces the URI validated at /authorize. A signed-in user must open the supplied links and approve a trusted client, after which the authorization token is sent to the attacker-controlled redirect URI.

CVSS severity9.1
Critical
EPSS probability2.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Mass assignment in MITREid Connect 1.3.3 and earlier allows remote attackers to steal OAuth tokens via crafted confirmation links. The /oauth/confirm_access handler binds HTTP query fields into the session-backed authorizationRequest, so an attacker-supplied redirectUri replaces the URI validated at /authorize. A signed-in user must open the supplied links and approve a trusted client, after which the authorization token is sent to the attacker-controlled redirect URI.

The record

CVE
CVE-2021-27582
Published
Feb 23, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-1321, T1528
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 23, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.4NVDAV:N/AC:L/Au:N/C:P/I:P/A:N
9.1NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
T1528Steal Application Access Token

Public exploit references

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Technologies

Your stack

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Your stack

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