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 0.35% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2025
CVE-2025-53856High confidence
TMM vulnerability
F5 · BIG-IP
Official source article: F5 K000156707 ↗. Check the applicable product and release in the original source.
8.7HighCVSS 4.0
Within 7 days
Mitigation availableHigh technical severity; prioritise exposed affected systems while verifying vendor guidance.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityHigh→Operational priority:High, 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 BIG-IP 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.
High technical severity; prioritise exposed affected systems while verifying vendor guidance.
Mitigation available01
What, why and how
When a virtual server, network address translation (NAT) object, or secure network address translation (SNAT) object uses the embedded Packet Velocity Acceleration (ePVA) feature, undisclosed traffic can cause the Traffic Management Microkernel (TMM) to terminate. To determine which BIG-IP platforms have an ePVA chip refer to K12837: Overview of the ePVA feature https://my.f5.com/manage/s/article/K12837 . Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
What
When a virtual server, network address translation (NAT) object, or secure network address translation (SNAT) object uses the embedded Packet Velocity Acceleration (ePVA) feature, undisclosed traffic can cause the Traffic Management Microkernel (TMM) to terminate. To determine which BIG-IP platforms have an ePVA chip refer to K12837: Overview of the ePVA feature https://my.f5.com/manage/s/article/K12837 . Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
Why
The product does not properly return control flow to the proper location after it has completed a task or detected an unusual condition.
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
When a virtual server, network address translation (NAT) object, or secure network address translation (SNAT) object uses the embedded Packet Velocity Acceleration (ePVA) feature, undisclosed traffic can cause the Traffic Management Microkernel (TMM) to terminate. To determine which BIG-IP platforms have an ePVA chip refer to K12837: Overview of the ePVA feature https://my.f5.com/manage/s/article/K12837 . Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
Why
The product does not properly return control flow to the proper location after it has completed a task or detected an unusual condition.
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 → Incorrect Control Flow Scoping → 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
- Low: no specialised conditions are recorded
- Security boundary
- Not a CVSS 4.0 base metric
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-705 ↗
CWE-705: Incorrect Control Flow Scoping. The product does not properly return control flow to the proper location after it has completed a task or detected an unusual condition.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:NCommon Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.ATNoneAttack requirements: No additional deployment or execution condition is required.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.VCNoneVulnerable-system confidentiality: No direct loss is represented by this metric.VINoneVulnerable-system integrity: No direct loss is represented by this metric.VAHighVulnerable-system availability: A successful attack can cause a major loss.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SANoneSubsequent-system availability: 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
- F5 Networks heeft updates uitgebracht om de kwetsbaarheden te verhelpen. Zie bijgevoegde referenties voor meer informatie. Aanvullend op bovengenoemd beveiligingsadvies heeft F5 Networks een websitebericht gepubliceerd over een beveiligingsincident op hun systemen. F5 Networks adviseert klanten hierin de laatste beveiligingsupdates zo snel mogelijk te installeren. Daarnaast heeft F5 Networks detectie- en hardeningmaatregelen gedeeld, en adviseert het bedrijf deze maatregelen in te zetten. Lees het websitebericht voor meer informatie. **UPDATE 27/01/2026** F5 heeft een update geplaatst op de website betreffende CVE-2025-53521. Het NCSC heeft waargenomen dat er misbruik is gemaakt van deze kwetsbaarheid.
- Workaround
- No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04
Evidence and provenance
Published 15 Oct 2025 · Last source change 26 Feb 2026, 16:57 UTC · CWE-705 · Incorrect Control Flow Scoping
CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source FIRST · tracked since 2026-08-14
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2025-34637
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD enriched
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
- Remediation statusRemediation status changed from Awaiting fix to Mitigation available.NCSC-NL ↗
- Before
- Awaiting fix
- After
- Mitigation available
CVE published
Remediation guidance 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.