Security readout for executives and security teams
Plain-English summary
This flaw lets certain Cisco Firepower security products miss malicious content if it is obfuscated with NULL characters. The device may allow traffic it was expected to block, exposing protected systems to downstream attacks. The CVSS score is medium, but business impact depends on whether Firepower is relied on as a key filtering control.
Executive priority
Treat as a moderate-priority network security control issue. It does not show confirmed active exploitation in the provided sources, but it weakens filtering controls that may protect high-value systems. Prioritize remediation where Firepower is a primary prevention layer.
Technical view
CVE-2019-1981 is a normalization weakness in Cisco Firepower Threat Defense, FirePOWER Services for ASA, and Firepower Management Center. An unauthenticated remote attacker could send specially obfuscated text-based payloads through an affected device and bypass filtering protections. The reported CVSS v3.0 score is 5.8.
Likely exposure
Exposure is likely limited to environments using the named Cisco Firepower products in traffic inspection or filtering paths. The source bundle does not identify specific affected versions, deployment modes, or fixed releases, so exposure requires checking Cisco’s advisory against installed software.
Exploitation context
The source describes remote, unauthenticated exploitation with low attack complexity and no user interaction. Exploitation requires traffic to pass through an affected device. CISA KEV is false in the provided data, and no cited source confirms active exploitation.
Researcher notes
The provided evidence establishes product family, attack preconditions, impact, and CVSS. It does not include affected version ranges, fixed versions, workaround details, or observed exploitation. Avoid assuming exploit availability or remediation specifics beyond Cisco guidance.
Mitigation direction
- Check Cisco’s advisory for affected releases and fixed software.
- Prioritize updates for Firepower devices protecting critical network segments.
- Confirm filtering policies do not rely on affected inspection alone.
- Use layered endpoint and gateway controls for malicious payload detection.
- Monitor Cisco guidance for workaround or upgrade instructions.
Validation and detection
- Inventory Cisco Firepower Threat Defense deployments.
- Identify FirePOWER Services for ASA and Firepower Management Center instances.
- Compare installed versions with Cisco’s advisory.
- Confirm affected devices sit in inspected traffic paths.
- Review change records for completed Cisco-directed updates.
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
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-264: 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.
Open ATT&CK lookupCVE-2019-1981 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
- 20190816 Cisco Firepower Threat Defense Software NULL Character Obfuscation Detection 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.
Permissions, Privileges, and Access Controls
Permissions, Privileges, and Access Controls represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.