Unauthenticated traffic interruption via TMM use-after-free
Published May 13, 2026 · Updated May 13, 2026
Use-after-free in F5 BIG-IP PEM iRules allows remote attackers to terminate TMM and interrupt traffic via crafted network traffic. TMM processes traffic against a freed object when an affected PEM iRule runs, but F5 has not disclosed the object, code path, or trigger. The condition requires a virtual server using affected PEM iRule commands; termination interrupts traffic without reported data disclosure or modification.
Summary
What happened
Use-after-free in F5 BIG-IP PEM iRules allows remote attackers to terminate TMM and interrupt traffic via crafted network traffic. TMM processes traffic against a freed object when an affected PEM iRule runs, but F5 has not disclosed the object, code path, or trigger. The condition requires a virtual server using affected PEM iRule commands; termination interrupts traffic without reported data disclosure or modification.
The record
- CVE
- CVE-2026-41218
- Published
- May 13, 2026
- Updated
- May 13, 2026
- Vendor
- F5 Networks
- Product
- BIG-IP
- Classifications
- CWE-416, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 13, 2026CVE publishedPublication date reported by the CVE source.
- 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.
- Affected versionversion=16.1.0 <*
- Affected versionversion=17.1.0 <17.1.3.1
- Affected versionversion=17.5.0 <17.5.1.4
- Affected versionversion=21.0.0 <21.0.0.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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