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CVE Record

CVE-2019-12706: Cisco Email Security Appliance Filter Bypass Vulnerability

A vulnerability in the Sender Policy Framework (SPF) functionality of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass the configured user filters on an affected device. The vulnerability exists because the affected software insufficiently validates certain incoming SPF messages. An attacker could exploit this vulnerability by sending a custom SPF packet to an affected device. A successful exploit could allow the attacker to bypass the configured header filters, which could allow malicious content to pass through the device.

MediumCVSS 6.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

Cisco ESA email gateways may fail to enforce configured user/header filters when processing certain SPF-related email traffic. In business terms, malicious email content could slip past filtering controls that teams expect to block it.

Executive priority

Treat this as a moderate email security control weakness. Prioritize remediation where ESA is internet-facing or blocks phishing, malware, or policy-sensitive inbound mail.

Technical view

CVE-2019-12706 is an input validation flaw in Cisco AsyncOS SPF functionality for Cisco Email Security Appliance. An unauthenticated remote attacker could cause configured header filters to be bypassed, potentially allowing malicious content through. CVSS 3.0 is 6.5 medium.

Likely exposure

Exposure is limited to organizations using Cisco Email Security Appliance with affected AsyncOS software and configured user or header filters. The provided sources do not specify affected release ranges.

Exploitation context

The source bundle does not show known active exploitation, and KEV is false. The attack is described as remote and unauthenticated, with low complexity, but the provided sources do not include public exploit evidence.

Researcher notes

Evidence supports CWE-20 input validation weakness in SPF handling. Affected versions and specific fixes are not included in the source bundle, so validation should begin with Cisco advisory mapping rather than assumptions.

Mitigation direction

  • Review Cisco’s advisory for affected and fixed AsyncOS releases.
  • Update affected Cisco ESA systems according to Cisco guidance.
  • Check whether SPF and header filtering are relied on for inbound mail controls.
  • Monitor inbound mail for filter bypass indicators until remediated.

Validation and detection

  • Inventory all Cisco ESA appliances and AsyncOS versions.
  • Confirm whether configured header filters are active on each appliance.
  • Compare appliance versions against Cisco’s advisory.
  • Review mail security logs for unexpected filter bypass behavior.
Prepared
Confidence
medium
Sources
3

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · low confidence lookup

CWE-20: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2019-12706 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
6.5 (3.0)
Known Exploited
No
Published

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

Official CVE source material

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.

1CVSS vectors
0Timeline events
0ADP providers
2Source links

CVSS vector scores

1 official score

We 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.

ScoreVersionSeverityVectorExploitImpactSource
6.5CVSS 3.0MediumCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N3.92.5Primary CVE score

Vulnerability scoring details

Base CVSS 3.0 score

6.5Medium
CVSS 3.0 vector shape for CVE-2019-12706Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
CiscoCisco Email Security Appliance (ESA)unspecifiedListed
Weakness

CWE details

CWE-20

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-20 · source CWE mapping

Improper Input Validation

Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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