CVE-2020-35112Public exploitNetwork attack vector

Executable launch via extensionless download name collision

Published Jan 7, 2021 · Updated Aug 4, 2024

Improper file handling in Firefox before 84, Firefox ESR before 78.6, and Thunderbird before 78.6 allows attackers to launch local executables. On Windows, the downloads panel asks the operating system to open an extensionless file by path, allowing executable-extension resolution to select a same-named .bat or .exe file in the download directory instead. The user must open the extensionless download while the colliding executable is already present, after which that executable runs with the user’s privileges.

CVSS severity8.8
High
EPSS probability1.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper file handling in Firefox before 84, Firefox ESR before 78.6, and Thunderbird before 78.6 allows attackers to launch local executables. On Windows, the downloads panel asks the operating system to open an extensionless file by path, allowing executable-extension resolution to select a same-named .bat or .exe file in the download directory instead. The user must open the extensionless download while the colliding executable is already present, after which that executable runs with the user’s privileges.

The record

CVE
CVE-2020-35112
Published
Jan 7, 2021
Updated
Aug 4, 2024
Vendor
Mozilla
Product
Firefox
Classifications
T1204.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 7, 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=unspecified <84

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <84
Mozilla · Thunderbirdversion=unspecified <78.6
Mozilla · Firefox ESRversion=unspecified <78.6

Published CVSS scores

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

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

T1204.002Malicious File

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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