CVE-2021-38510Public exploitNetwork attack vector

Command execution via omitted .inetloc warning

Published Dec 8, 2021 · Updated Aug 4, 2024

Download-protection bypass in Mozilla Firefox before 94, Firefox ESR before 91.3, and Thunderbird before 91.3 allows attackers to run commands. The macOS file-handling lists omitted the .inetloc extension, so downloads avoided the executable-file warning even though crafted inetloc files can invoke file URLs. Exploitation requires macOS and a user to open a downloaded crafted file; other operating systems are unaffected.

CVSS severity8.8
High
EPSS probability1.00%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Download-protection bypass in Mozilla Firefox before 94, Firefox ESR before 91.3, and Thunderbird before 91.3 allows attackers to run commands. The macOS file-handling lists omitted the .inetloc extension, so downloads avoided the executable-file warning even though crafted inetloc files can invoke file URLs. Exploitation requires macOS and a user to open a downloaded crafted file; other operating systems are unaffected.

The record

CVE
CVE-2021-38510
Published
Dec 8, 2021
Updated
Aug 4, 2024
Vendor
Mozilla
Product
Firefox
Classifications
T1204.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 8, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <94

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <94
Mozilla · Thunderbirdversion=unspecified <91.3
Mozilla · Firefox ESRversion=unspecified <91.3

Published CVSS scores

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST NVDAV: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

T1204.002User Execution Malicious File

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo