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OS Command InjectionWeakness · CWE-78

CVE-2021-46686

CRITICAL · 9.8 CVSS v3.0 Published 2025-02-18
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Improper neutralization of special elements used in an OS command ('OS Command Injection') issue exists in acmailer CGI ver.4.0.3 and earlier and acmailer DB ver.1.1.5 and earlier. If this vulnerability is exploited, an arbitrary OS command may be executed by an attacker.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

OS command injection vulnerability in acmailer CGI ver.4.0.3 and earlier and acmailer DB ver.1.1.5 and earlier. The application fails to properly sanitize user input before passing it to OS-level command execution functions, allowing remote attackers to inject and execute arbitrary OS commands. This is a critical remote code execution (RCE) flaw with network-exploitable attack vector.

MitigationUpgrade to patched versions of acmailer CGI (after 4.0.3) and acmailer DB (after 1.1.5). If immediate patching is not feasible, restrict network access to the CGI endpoints and disable any unnecessary command execution functions at the host level.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify acmailer CGI installation
    Locate the acmailer CGI application files and retrieve the version number from the application's main script, configuration, or version file
    Affected if The installed version is 4.0.3 or earlier
  2. Identify acmailer DB installation
    Locate the acmailer DB application files and retrieve the version number from the application's main script, configuration, or version file
    Affected if The installed version is 1.1.5 or earlier
  3. Verify CGI endpoint exposure
    Determine if the acmailer CGI interface is accessible over the network by checking web server configuration for CGI script mappings and testing endpoint availability
    Affected if The CGI endpoints are externally accessible and accept user-supplied input
  4. Check for user input handling
    Review the application's configuration to confirm that user-submitted data is processed and can reach the underlying system call functions
    Affected if User input fields are processed without sanitization before command execution

You are affected if acmailer CGI version 4.0.3 or earlier OR acmailer DB version 1.1.5 or earlier is installed AND the CGI interface accepts user input that reaches command execution functions.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade to patched versions of acmailer CGI (after 4.0.3) and acmailer DB (after 1.1.5). If immediate patching is not feasible, restrict network access to the CGI endpoints and disable any unnecessary command execution functions at the host level.

Recommended fix High confidence

acmailer CGI 4.0.4+ or acmailer DB 1.1.6+

  1. 1. Identify the currently installed acmailer version (CGI or DB) by checking the application files or administration panel.
  2. 2. For acmailer CGI users: Download acmailer CGI version 4.0.4 or later from the official vendor website (acmailer.jp).
  3. 3. For acmailer DB users: Download acmailer DB version 1.1.6 or later from the official vendor website (acmailer.jp).
  4. 4. Back up the current installation, including all configuration files, databases, and mail data.
  5. 5. Stop the web server or mail service to prevent access during the upgrade process.
  6. 6. Replace the old application files with the new version files, preserving configuration files where instructed by the vendor.
  7. 7. Verify file permissions are correctly set after the upgrade.
  8. 8. Restart the web server or mail service.
Caveat Review vendor release notes for any configuration changes or deprecated features between versions

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA3.0 h
21.0 hours of engineering $3,680
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-46686 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data