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Axis OsOperating system · Axis

CVE-2021-31986

MEDIUM · 6.8 CVSS v3.1 Published 2021-10-05
Fix available
A fix is available. Upgrade to 6.50.5.5 / 8.40.4.3 or later.
See remediation →
75/100
Remediation priority · High
Remotely reachable No privileges

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
User controlled parameters related to SMTP notifications are not correctly validated. This can lead to a buffer overflow resulting in crashes and data leakage.

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

A buffer overflow vulnerability exists in the SMTP notification functionality where user-controlled parameters are not properly validated before use. This allows attackers to potentially crash the service or leak data through malformed input to SMTP-related parameters.

MitigationImplement strict input validation and bounds checking on all SMTP notification parameters. Ensure all user inputs are validated for length, format, and content before being used in any string operations or buffer allocations.

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

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Axis OsOperating system
Affected:< 10.7
Axis Os 2016Operating system
Affected:< 6.50.5.5
Axis Os 2018Operating system
Affected:< 8.40.4.3
Axis Os 2020Operating system
Affected:< 9.80.3.5

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
High
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/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 the installed Axis OS version
    Access the device web interface and navigate to System > About, or use SSH to run the command 'show version' or 'cat /proc/axos/version' to retrieve the firmware version
    Affected if the installed version is less than 10.7, 6.50.5.5, 8.40.4.3, or 9.80.3.5 depending on the product line (2016, 2018, 2020, or current)
  2. Confirm SMTP notification functionality is configured
    Access the device web interface and navigate to Settings > Notifications > Email/SMTP, or check for SMTP-related configuration files via SSH in the /param/ directory
    Affected if SMTP notification is enabled and an SMTP server is configured with sender and recipient email addresses
  3. Review SMTP parameter configuration for long or malformed input
    Inspect the SMTP configuration settings including sender email, recipient email, SMTP server hostname, subject line, and any custom message fields for unusually long strings or unexpected characters
    Affected if any SMTP-related parameters contain input exceeding typical length limits or contain special characters not expected in their respective fields
  4. Monitor for service instability related to SMTP operations
    Check system logs via the web interface or SSH command 'log -f' for crashes, segmentation faults, or errors occurring immediately after SMTP notifications are triggered
    Affected if the service crashes or exhibits abnormal behavior when sending email notifications

The environment is affected if the Axis OS version falls below the specified thresholds AND SMTP notification functionality is enabled with user-supplied parameters.

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
Upgrade available Upgrade to 6.50.5.5 / 8.40.4.3 / 9.80.3.5 or later
Fixed in 6.50.5.58.40.4.39.80.3.5
Interim mitigation

Implement strict input validation and bounds checking on all SMTP notification parameters. Ensure all user inputs are validated for length, format, and content before being used in any string operations or buffer allocations.

Recommended fix High confidence

Axis OS 2016: >=6.50.5.5 | Axis OS 2018: >=8.40.4.3 | Axis OS 2020: >=9.80.3.5 | Axis OS 10.x: >=10.7

  1. Identify the current Axis OS version running on the device
  2. Determine which version branch the device is on (2016, 2018, 2020, or 10.x)
  3. For Axis OS 2016 devices: upgrade to version 6.50.5.5 or later
  4. For Axis OS 2018 devices: upgrade to version 8.40.4.3 or later
  5. For Axis OS 2020 devices: upgrade to version 9.80.3.5 or later
  6. For Axis OS (current branch): upgrade to version 10.7 or later
  7. After upgrade, verify the SMTP notification configuration works correctly
Caveat Standard firmware upgrade risks apply - ensure backup of configuration and review release notes for any feature changes

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

Fix this in Axis Os Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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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-2021-31986 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