CVE-2020-6399Public exploitNetwork attack vector

Cross-origin data disclosure via AppCache redirect oracle

Published Feb 11, 2020 · Updated Aug 4, 2024

Insufficient AppCache policy enforcement in Google Chrome before 80.0.3987.87 allows remote attackers to leak cross-origin data. The AppCache manifest handler exposes redirect outcomes through cache success and failure events, creating an oracle that reveals cross-origin URL data. Exploitation requires a user to load a crafted HTML page; the demonstrated attack recovers redirect URLs containing session or CSRF tokens without changing data.

CVSS severity6.5
Medium
EPSS probability1.99%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insufficient AppCache policy enforcement in Google Chrome before 80.0.3987.87 allows remote attackers to leak cross-origin data. The AppCache manifest handler exposes redirect outcomes through cache success and failure events, creating an oracle that reveals cross-origin URL data. Exploitation requires a user to load a crafted HTML page; the demonstrated attack recovers redirect URLs containing session or CSRF tokens without changing data.

The record

CVE
CVE-2020-6399
Published
Feb 11, 2020
Updated
Aug 4, 2024
Vendor
Google Cloud
Product
Google Chrome
Classifications
CWE-20
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 11, 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=unspecified <80.0.3987.87

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Google Cloud · Google Chromeversion=unspecified <80.0.3987.87

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:P/I:N/A:N
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/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 exploitPublished

Weakness, pattern, technique

CWE-20Improper Input Validation

Public exploit references

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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