CVE-2020-27847Network attack vector

Unauthenticated identity impersonation via XML round-trip mutation

Published May 28, 2021 · Updated Aug 4, 2024

Authentication bypass in the SAML connector in Dex before 2.27.0 allows remote attackers to assume another user’s identity. Dex validates a transformed SAML response but serializes attacker-controlled XML again; XML round-trip mutations can preserve a valid signature while changing the asserted identity. The SAML connector must be configured and reachable, after which the forged identity can obtain tokens accepted by applications that trust Dex.

CVSS severity9.8
Critical
EPSS probability1.72%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in the SAML connector in Dex before 2.27.0 allows remote attackers to assume another user’s identity. Dex validates a transformed SAML response but serializes attacker-controlled XML again; XML round-trip mutations can preserve a valid signature while changing the asserted identity. The SAML connector must be configured and reachable, after which the forged identity can obtain tokens accepted by applications that trust Dex.

The record

CVE
CVE-2020-27847
Published
May 28, 2021
Updated
Aug 4, 2024
Vendor
Dex
Product
Dex
Classifications
CWE-228, T1606.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 28, 2021CVE 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=dex 2.27.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Dex · Dexversion=dex 2.27.0

Published CVSS scores

7.5NIST NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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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 exploitUnconfirmed

Weakness, pattern, technique

CWE-228Improper Handling of Syntactically Invalid Structure
T1606.002Forge Web Credentials: SAML Tokens

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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