How severe is CVE-2025-26621?

CVE-2025-26621 has a CVSS 3.x base score of 7.6, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability high.

Is CVE-2025-26621 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (27th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-26621?

CVE-2025-26621 affects Citeum Opencti. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-26621?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2025-26621 have an EU (EUVD) identifier?

Yes. CVE-2025-26621 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-15725.

When was CVE-2025-26621 published?

CVE-2025-26621 was published on 2025-05-19 and last updated on 2026-06-17.

CVE-2025-26621

CVE-2025-26621 is a high-severity vulnerability in Citeum Opencti with a CVSS 3.x base score of 7.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-1321.

Key facts

Severity: High (CVSS 3.x base score 7.6)
EPSS exploit prediction: 0% (27th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-15725
Weakness: CWE-1321
Affected product: Citeum Opencti
Published: 2025-05-19
Last modified: 2026-06-17

Description

OpenCTI is an open source platform for managing cyber threat intelligence knowledge and observables. Prior to version 6.5.2, any user with the capability manage customizations can edit webhook that will execute javascript code. This can be abused to cause a denial of service attack by prototype pollution, making the node js server running the OpenCTI frontend become unavailable. Version 6.5.2 fixes the issue.

Frequently asked questions

What is CVE-2025-26621?: OpenCTI is an open source platform for managing cyber threat intelligence knowledge and observables. Prior to version 6.5.2, any user with the capability manage customizations can edit webhook that will execute javascript code. This can be abused to cause a denial of service attack by prototype pollution, making the node js server running the OpenCTI frontend become unavailable. Version 6.5.2 fixes the issue.
How severe is CVE-2025-26621?: CVE-2025-26621 has a CVSS 3.x base score of 7.6, rated high severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability high.
Is CVE-2025-26621 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (27th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-26621?: CVE-2025-26621 affects Citeum Opencti. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-26621?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2025-26621 have an EU (EUVD) identifier?: Yes. CVE-2025-26621 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-15725.
When was CVE-2025-26621 published?: CVE-2025-26621 was published on 2025-05-19 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:citeum:opencti:*:*:*:*:*:*:*:*

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