CVE-2026-39455Network attack vector

Unauthenticated service interruption via file descriptor exhaustion

Published May 13, 2026 · Updated May 13, 2026

Resource exhaustion in the F5 BIG-IP Configuration utility allows remote attackers to interrupt service via undisclosed traffic. The httpd process fails to release file descriptors after handling that traffic, eventually exhausting its available descriptor pool; F5 has not disclosed the request pattern. Reachability requires LDAP authentication to be configured for the utility, and exploitation affects availability without reported data access or modification.

CVSS severity8.7
High
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in the F5 BIG-IP Configuration utility allows remote attackers to interrupt service via undisclosed traffic. The httpd process fails to release file descriptors after handling that traffic, eventually exhausting its available descriptor pool; F5 has not disclosed the request pattern. Reachability requires LDAP authentication to be configured for the utility, and exploitation affects availability without reported data access or modification.

The record

CVE
CVE-2026-39455
Published
May 13, 2026
Updated
May 13, 2026
Vendor
F5 Networks
Product
BIG-IP
Classifications
CWE-772, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 13, 2026CVE publishedPublication date reported by the CVE source.
  2. May 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=16.1.0 <*
  2. Affected versionversion=17.1.0 <17.1.3.2
  3. Affected versionversion=17.5.0 <17.5.1.6
  4. Affected versionversion=21.0.0 <21.0.0.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

F5 Networks · BIG-IPversion=16.1.0 <*; version=17.1.0 <17.1.3.2; version=17.5.0 <17.5.1.6; version=21.0.0 <21.0.0.2

Published CVSS scores

8.7F5 NetworksCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
7.5F5 NetworksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-772Missing Release of Resource after Effective Lifetime
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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