Security readout for executives and security teams
Plain-English summary
This issue lets a remote sender get a specially formed MP3 attachment past Cisco ESA content filters that should drop the email. It does not indicate mailbox compromise or appliance takeover, but it can weaken email controls that organizations rely on to enforce attachment policy.
Executive priority
Treat as a moderate email-security control bypass. Prioritize organizations that rely on Cisco ESA attachment filtering for policy enforcement or threat reduction, but do not rank it like a system takeover vulnerability based on the provided evidence.
Technical view
Cisco AsyncOS for Cisco Email Security Appliance has improper validation in its MP3 detection engine. An unauthenticated remote attacker can send a crafted MP3 through the device and bypass configured content filters that would normally drop the email. The CVSS score is 5.8 with low integrity impact.
Likely exposure
Exposure is likely limited to organizations using Cisco ESA with content filters that inspect or block MP3 file types. The source bundle does not specify affected AsyncOS versions or CPEs, so inventory confirmation against Cisco guidance is required.
Exploitation context
The source describes remote, unauthenticated exploitation by sending a crafted MP3 file through the targeted ESA. The bundle does not report public exploitation, and CISA KEV status is false, so active exploitation should not be assumed.
Researcher notes
The issue maps to CWE-20 and affects MP3 file-type validation in Cisco ESA’s detection engine. The bundle lists affected versions as unspecified, so version-scoped exposure and remediation details must come from the Cisco advisory or vendor support.
Mitigation direction
- Check Cisco’s advisory for affected AsyncOS releases and vendor-supported fixes.
- Apply Cisco-recommended updates or configuration changes where applicable.
- Identify ESA filters that depend on MP3 detection or attachment dropping.
- Add temporary attachment review or quarantine controls if MP3 blocking is business-critical.
Validation and detection
- Inventory Cisco ESA appliances and their AsyncOS versions.
- Confirm whether MP3 content filters are configured to drop email.
- Compare appliance versions and configuration against Cisco’s advisory.
- Review mail security logs for unusual MP3 attachment delivery patterns.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
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CWE-20: Exact CWE lookup
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Open ATT&CK lookupCVE-2019-15971 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.8 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N3.91.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
5.8MediumVector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- 20191120 Cisco Email Security Appliance MP3 Content Filter Bypass VulnerabilityCVE reference · vendor-advisory, x_refsource_CISCO
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.