CVE-2020-6806Public exploitNetwork attack vector

Memory corruption via promise-driven array resize

Published Mar 25, 2020 · Updated Aug 4, 2024

Out-of-bounds read in Mozilla Firefox, Firefox ESR, and Thunderbird allows remote attackers to corrupt memory through crafted script. BodyStream::OnInputStreamReady permits promise callbacks to resize a ReadableStream array during execution, then reads beyond its new end. A user must process attacker-controlled script in a browser-like context; Thunderbird mail reading disables scripting, and successful triggering can crash the application.

CVSS severity8.8
High
EPSS probability2.61%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in Mozilla Firefox, Firefox ESR, and Thunderbird allows remote attackers to corrupt memory through crafted script. BodyStream::OnInputStreamReady permits promise callbacks to resize a ReadableStream array during execution, then reads beyond its new end. A user must process attacker-controlled script in a browser-like context; Thunderbird mail reading disables scripting, and successful triggering can crash the application.

The record

CVE
CVE-2020-6806
Published
Mar 25, 2020
Updated
Aug 4, 2024
Vendor
Mozilla
Product
Firefox
Classifications
CWE-125, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 25, 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 <74
  2. Affected versionversion=unspecified <ESR68.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <74; version=unspecified <ESR68.6
Mozilla · Thunderbirdversion=unspecified <68.6
Mozilla · Firefox ESRversion=unspecified <68.6

Published CVSS scores

8.8NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST National Vulnerability DatabaseAV:N/AC:M/Au:N/C:P/I:P/A:P

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 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-125Out-of-bounds Read
T1203Exploitation for Client Execution

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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