CVE-2026-42781

Service interruption via nonterminating ePVA traffic processing

Published May 13, 2026 · Updated May 13, 2026

Denial of service in F5 BIG-IP FastL4 virtual servers allows remote attackers to interrupt service via local Ethernet traffic. F5 maps the flaw to an infinite loop but does not disclose the traffic pattern or ePVA/TMM processing locus that fails to terminate. Reachability requires adjacent-network access to affected hardware and an ePVA-offloaded FastL4 profile; no confidentiality or integrity impact is reported.

CVSS severity7.1
High
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in F5 BIG-IP FastL4 virtual servers allows remote attackers to interrupt service via local Ethernet traffic. F5 maps the flaw to an infinite loop but does not disclose the traffic pattern or ePVA/TMM processing locus that fails to terminate. Reachability requires adjacent-network access to affected hardware and an ePVA-offloaded FastL4 profile; no confidentiality or integrity impact is reported.

The record

CVE
CVE-2026-42781
Published
May 13, 2026
Updated
May 13, 2026
Vendor
F5 Networks
Product
BIG-IP
Classifications
CWE-835, T1499.004
Attack vector
adjacent
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=17.1.0 <17.1.3.1
  2. Affected versionversion=17.5.0 <17.5.1.4
  3. Affected versionversion=21.0.0 <21.0.0.1

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

F5 Networks · BIG-IPversion=17.1.0 <17.1.3.1; version=17.5.0 <17.5.1.4; version=21.0.0 <21.0.0.1

Published CVSS scores

7.1F5 NetworksCVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
6.5F5 NetworksCVSS:3.1/AV:A/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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499.004Application or System Exploitation

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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