Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessIdentify BIG-IP management interface
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DeliverySend crafted traffic to LDAP auth endpoint
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ExploitTrigger file descriptor leak in httpd
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ExecutionExhaust descriptor pool
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ImpactManagement interface denial of service
Vulnerability Assessment
| Weakness |
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Resource cleanup on lifecycle end
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| Exploitation Conditions | BIG-IP Configuration utility must be explicitly configured to use Lightweight Directory Access Protocol (LDAP) for authentication (not the default local authentication mode). The attack targets network-accessible management interfaces, so the Configuration utility must be reachable from the attacker's network position. Default BIG-IP installations using local authentication or other authentication methods (RADIUS, TACACS+, Active Directory via other mechanisms) are NOT vulnerable. The vendor redacted specific traffic patterns as 'undisclosed,' suggesting the exploit may require knowledge of specific LDAP authentication flow characteristics. Exploitation is limited to causing management plane denial of service - data plane traffic processing (actual load balancing, proxying, firewall functions) remains unaffected, and no data exfiltration or code execution is possible (CVSS C:N/I:N). |
| Impact | The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) indicates a remotely exploitable denial-of-service vulnerability requiring no authentication, low attack complexity, and no user interaction - meeting SSVC 'automatable' criteria. However, real-world risk is significantly constrained by the exploitation condition: LDAP authentication must be explicitly configured for the Configuration utility, which is not a default deployment mode for most BIG-IP installations. The 7.5 CVSS score reflects maximum potential impact but does not account for this prerequisite. Absence from CISA KEV suggests targeted rather than opportunistic exploitation. The vulnerability impacts management plane availability only (Configuration utility), not data plane traffic processing, limiting business impact to administrative operations. Priority should be high for environments using LDAP-authenticated management access, moderate for default deployments where the condition is not met. Key missing data: EPSS score unavailable, specific affected version ranges not provided in CVE data, exploit complexity details redacted by vendor ('undisclosed traffic'). |
| Exploit ScenarioDerived | An external attacker identifies a BIG-IP management interface accessible over the internet (common in cloud deployments or poorly segmented networks). By sending specially crafted traffic patterns to the Configuration utility's LDAP-authenticated login interface, the attacker triggers file descriptor leaks in the httpd process. Over minutes to hours, the descriptor pool exhausts, causing the Configuration utility to become unresponsive and preventing legitimate administrators from accessing the management interface until the httpd process is restarted. No public proof-of-concept code identified at time of analysis. |
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Alert meAnalysisAIv1 – May 13, 2026
Resource exhaustion in BIG-IP Configuration utility allows remote unauthenticated attackers to trigger file descriptor exhaustion in the httpd process when LDAP authentication is enabled. The attack achieves complete denial of service (CVSS A:H) through network-accessible undisclosed traffic patterns. F5 has released patches addressing this vulnerability. EPSS data not available, not listed in CISA KEV, indicating no confirmed widespread exploitation at time of analysis.
RemediationAI
Apply vendor-released patches documented in F5 Security Advisory K000160874 (https://my.f5.com/manage/s/article/K000160874), which specifies exact fixed versions for supported BIG-IP releases. If immediate patching is not feasible, implement compensating controls specific to this attack vector: restrict network access to the Configuration utility to trusted management networks only via firewall rules or BIG-IP's built-in management interface ACLs, reducing attack surface to internal administrators. Alternatively, switch from LDAP authentication to local authentication or RADIUS/TACACS+ if operationally acceptable, which eliminates the vulnerable code path entirely - though this may impact centralized identity management workflows. Monitor httpd process file descriptor usage via 'lsof -p <httpd_pid> | wc -l' and configure alerting for abnormal growth approaching system limits. Note that access restriction does not fix the underlying resource leak but significantly reduces exploitability from AV:N to AV:A (adjacent network) or AV:L (local) in practice.
Affected VersionsENISA
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in euvd
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Technical ContextAI · show details
This vulnerability stems from CWE-772 (Missing Release of Resource after Effective Lifetime), specifically affecting file descriptor management in the httpd daemon of F5 BIG-IP Configuration utility. When LDAP authentication is configured for the management interface, certain traffic patterns cause the httpd process to leak or fail to release file descriptors - the kernel-level handles for open network connections, files, and sockets. Unix-like systems have per-process file descriptor limits (typically ulimit -n), and exhausting this pool prevents the process from accepting new connections or opening files, effectively disabling the Configuration utility. The affected CPE (cpe:2.3:a:f5:big-ip) indicates the application-layer Configuration utility specifically, not the underlying BIG-IP system software in general. The F5 advisory K000160874 provides vendor-confirmed details on affected versions and remediation.
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Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Primary rating from Vendor (f5) · only source for this CVE.
CVSS VectorVendor: f5
Lifecycle Timeline
2DescriptionCVE.org
When the BIG-IP Configuration utility is configured to use Lightweight Directory Access Protocol (LDAP) authentication, undisclosed traffic can cause the httpd process to exhaust the available file descriptors. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
Executive ViewAI
CVE-2026-39455 is a high-severity denial-of-service vulnerability in F5 BIG-IP Configuration utility that allows unauthenticated remote attackers to exhaust system resources and completely disable the affected device when LDAP authentication is enabled. Organizations running vulnerable BIG-IP instances face immediate risk of service unavailability, impacting network access and potentially critical business operations dependent on load balancing or application delivery.
Apply vendor patch. If immediate patching is unavailable, temporarily disable LDAP authentication if operationally feasible, or restrict network access to BIG-IP Configuration utility through firewall rules limiting connections to trusted administrative networks only.
Threat Intelligence Overview
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.
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EUVD-2026-29966
GHSA-6225-9whv-x529
NVD
CVE.org
EPSS
Vulnrichment
VulDB
Exploit-DB