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Email Security ApplianceApplication · Cisco

CVE-2022-20960

HIGH · 7.5 CVSS v3.1 Published 2022-11-04
Fix available
A fix is available. Upgrade to 14.2.1-015 / 14.3.0-020 or later.
See remediation →
84/100
Remediation priority · High
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
A vulnerability in Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper handling of certain TLS connections that are processed by an affected device. An attacker could exploit this vulnerability by establishing a large number of concurrent TLS connections to an affected device. A successful exploit could allow the attacker to cause the device to drop new TLS email messages that come from the associated email servers. Exploitation of this vulnerability does not cause the affected device to unexpectedly reload. The device will recover autonomously within a few hours of when the attack is halted or mitigated.

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 · high confidence

A vulnerability in Cisco AsyncOS Software for Cisco Email Security Appliance exists due to improper handling of certain TLS connections. An unauthenticated remote attacker can cause a DoS condition by establishing a large number of concurrent TLS connections to the affected device, causing it to drop new TLS email messages. The device recovers autonomously within a few hours but remains vulnerable to ongoing attacks.

MitigationApply the Cisco security patch/update for this vulnerability. In the interim, implement rate limiting or filtering on TLS connections at network perimeter to mitigate the attack volume.

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
Email Security ApplianceApplication
Affected:< 14.2.1-015>= 14.3.0, < 14.3.0-020

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
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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 device model
    Access the ESA web interface or CLI and confirm the device is a Cisco Email Security Appliance. Check the device model name and hardware type.
    Affected if The device is not a Cisco Email Security Appliance (this CVE only affects ESA)
  2. Check AsyncOS version
    In the ESA CLI, run the 'version' command or check via the web interface under System Administration > Software Update. Note the full version string including the build number (e.g., 14.2.1-015).
    Affected if The installed version is < 14.2.1-015 OR >= 14.3.0 but < 14.3.0-020
  3. Verify TLS is enabled
    Check the ESA mail flow configuration. In the web interface, go to Mail Policies > Inbound/Outbound MD. Verify that TLS is configured or enabled for email processing.
    Affected if TLS is enabled and the AsyncOS version is in the affected ranges
  4. Review TLS connection handling
    Monitor the ESA for symptoms of TLS connection exhaustion. Check logs for TLS handshake failures or connection drop messages. Use 'connectionstatus' or 'tlsconfig' commands in CLI if available.
    Affected if The device shows symptoms of TLS connection limits being reached or dropped TLS connections
  5. Check system uptime and recovery status
    If the device was recently experiencing TLS-related issues, verify current operational status. The device recovers autonomously within hours but remains vulnerable to repeat attacks.
    Affected if The device experienced TLS DoS symptoms and is running an affected version

You are affected if the device is a Cisco Email Security Appliance running AsyncOS version < 14.2.1-015 or >= 14.3.0 but < 14.3.0-020, with TLS enabled.

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 14.2.1-015 / 14.3.0-020 or later
Fixed in 14.2.1-01514.3.0-020
Interim mitigation

Apply the Cisco security patch/update for this vulnerability. In the interim, implement rate limiting or filtering on TLS connections at network perimeter to mitigate the attack volume.

Recommended fix High confidence

For ESA < 14.2.1-015: upgrade to 14.2.1-015 or later 14.2.x release; For ESA >= 14.3.0 < 14.3.0-020: upgrade to 14.3.0-020 or later 14.3.x release

  1. 1. Identify the current Cisco ESA AsyncOS version by accessing the ESA web interface or using the 'version' command in the CLI.
  2. 2. Determine the appropriate upgrade path based on current version: if running < 14.2.1-015, plan upgrade to 14.2.1-015 or later; if running >= 14.3.0 but < 14.3.0-020, plan upgrade to 14.3.0-020 or later.
  3. 3. Review Cisco ESA upgrade documentation and release notes for the target version to ensure compatibility.
  4. 4. Download the appropriate AsyncOS upgrade image from Cisco (requires valid support contract).
  5. 5. Schedule a maintenance window as upgrades may require brief downtime.
  6. 6. Upload the upgrade image via the ESA web interface (System Administration > Update > Upload Upgrade) or CLI.
  7. 7. Initiate the upgrade and confirm completion.
  8. 8. Verify the new version is running and that TLS processing is functioning normally.
Caveat ESA upgrades typically require brief downtime; ensure valid Cisco service contract for access to patches

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

Fix this in Email Security Appliance Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.

Scan for this in your stack

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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-2022-20960 in production — separate from our analysis above.

No notes yet

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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