CVE-2020-1056Network attack vector

Cross-domain data access and injection via policy failure

Published May 21, 2020 · Updated Aug 19, 2026

Cross-domain policy bypass in Microsoft Edge Legacy allows remote attackers to read and inject cross-domain content through a crafted webpage. EdgeHTML's cross-domain policy enforcement fails to keep attacker-controlled web content within its origin, while Microsoft has not disclosed the lower-level implementation defect. Exploitation requires a user to open attacker-controlled content, after which the browser exposes information from one domain and permits content injection into another.

CVSS severity8.1
High
EPSS probability2.09%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-domain policy bypass in Microsoft Edge Legacy allows remote attackers to read and inject cross-domain content through a crafted webpage. EdgeHTML's cross-domain policy enforcement fails to keep attacker-controlled web content within its origin, while Microsoft has not disclosed the lower-level implementation defect. Exploitation requires a user to open attacker-controlled content, after which the browser exposes information from one domain and permits content injection into another.

The record

CVE
CVE-2020-1056
Published
May 21, 2020
Updated
Aug 19, 2026
Vendor
Microsoft
Product
Microsoft Edge Legacy
Classifications
T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 21, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 19, 2026Record 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=1.0..0 <publication

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · Microsoft Edge Legacyversion=1.0..0 <publication

Published CVSS scores

5.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:N
8.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/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.

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

T1203Exploitation for Client Execution

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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