Evidence used
- No CISA KEV confirmation is currently recorded.
- The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
- EPSS is 0.78% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2018
CVE-2018-5538High confidence
F5 Networks, Inc. BIG-IP (DNS): security vulnerability
F5 Networks, Inc. · BIG-IP (DNS)
3.7LowCVSS 3.0
Scheduled
Mitigation availableLow technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityLow→Operational priority:Low, unchanged from published severity.unchanged
Compensating controls
- Apply the linked authoritative mitigation while planning the permanent fix.
- Restrict the affected network interface to trusted sources where business-safe.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs F5 Networks, Inc. BIG-IP (DNS) and falls inside the recorded affected range.
- Recheck the vendor advisory before scheduling a change because no verified fixed version is currently retained.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Low technical severity with no CISA KEV confirmation; remediate through the normal risk-based patch cycle unless local exposure raises the priority.
Mitigation available01
What, why and how
On F5 BIG-IP DNS 13.1.0-13.1.0.7, 12.1.3-12.1.3.5, DNS Express / DNS Zones accept NOTIFY messages on the management interface from source IP addresses not listed in the 'Allow NOTIFY From' configuration parameter when the db variable "dnsexpress.notifyport" is set to any value other than the default of "0".
What
On F5 BIG-IP DNS 13.1.0-13.1.0.7, 12.1.3-12.1.3.5, DNS Express / DNS Zones accept NOTIFY messages on the management interface from source IP addresses not listed in the 'Allow NOTIFY From' configuration parameter when the db variable "dnsexpress.notifyport" is set to any value other than the default of "0".
Why
The current structured CVE record identifies a security weakness, but the root cause requires confirmation in the linked vendor material.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
On F5 BIG-IP DNS 13.1.0-13.1.0.7, 12.1.3-12.1.3.5, DNS Express / DNS Zones accept NOTIFY messages on the management interface from source IP addresses not listed in the 'Allow NOTIFY From' configuration parameter when the db variable "dnsexpress.notifyport" is set to any value other than the default of "0".
Why
The current structured CVE record identifies a security weakness, but the root cause requires confirmation in the linked vendor material.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- a network path → vulnerable operation → cause the confidentiality, integrity or availability impact described by the vendor
- Attack surface
- Network
- Privileges required
- None: unauthenticated exploitation is possible
- User interaction
- None
- Attack complexity
- High: exploitation depends on specific conditions
- Security boundary
- Unchanged: impact remains within the vulnerable component's security authority
- Weakness
?
CWE means Common Weakness Enumeration. - CWE not yet assigned
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:NCommon Vulnerability Scoring System 3.0: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.ILowIntegrity impact: A successful attack can cause a limited loss.ANoneAvailability impact: No direct loss is represented by this metric.- Post-exploitation / living off the land
- No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Mitigation available
- Action
- Apply the mitigation in the linked authoritative guidance while planning the vendor's permanent fix.
- Workaround
- A mitigation or workaround reference is available from the source linked below; validate it against the affected product and version.
04
Evidence and provenance
Published 25 Jul 2018 · Last source change 17 Sept 2024, 03:38 UTC · CWE not yet assigned
CVE recordCVE.org · 5.1
CVSS sourceNIST NVD
EPSS source FIRST · tracked since 2026-09-01
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2018-17307
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceUnavailable
NVD statusNVD modified after enrichment
Missing structured fields: CWE classification. Missing data is not evidence of low risk; review the primary advisory.
Material change intelligence
View recent updates ↗What changed after publication
- ENISA EUVD mappingEUVD-2018-17307 was added to the official ENISA EUVD mapping for this CVE.ENISA EUVD ↗
- Before
- not recorded
- After
- {"euvdId":"EUVD-2018-17307"}
- Vendor guidanceAuthoritative vendor guidance changed: added mitigation: support.f5.com/K45435121; added remediation: support.f5.com/K45435121.support.f5.com ↗
- Before
- no authoritative guidance recorded
- After
- mitigation: support.f5.com/K45435121 · remediation: support.f5.com/K45435121
- Remediation statusRemediation status changed from Awaiting fix to Mitigation available.support.f5.com ↗
- Before
- Awaiting fix
- After
- Mitigation available
- SeveritySeverity changed from Unknown to Low.NIST NVD ↗
- Before
- Unknown
- After
- Low
- CVSS scoreCVSS score changed from not recorded to 3.7 (CVSS 3.0 · NIST NVD · CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N).NIST NVD ↗
- Before
- not recorded
- After
- 3.7 (CVSS 3.0 · NIST NVD · CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N)
- Catalogue recordCVE added to the BlackTree catalogue.CNA ↗
CVE published
Mitigation reference recorded
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.