CVE-2026-6621
CVE-2026-6621 is a high-severity vulnerability with a CVSS 3.x base score of 7.3. 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-94.
Key facts
- Severity: High (CVSS 3.x base score 7.3)
- CVSS v2: 7.5
- CVSS v4: 5.5
- EPSS exploit prediction: 0% (26th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-23812
- Weakness: CWE-94
- Published:
- Last modified:
Description
A vulnerability was determined in 1024bit extend-deep up to 0.1.6. The impacted element is an unknown function of the file index.js. This manipulation of the argument __proto__ causes improperly controlled modification of object prototype attributes. Remote exploitation of the attack is possible. The exploit has been publicly disclosed and may be utilized. The code repository of the project has not been active for many years.
Frequently asked questions
- What is CVE-2026-6621?
- A vulnerability was determined in 1024bit extend-deep up to 0.1.6. The impacted element is an unknown function of the file index.js. This manipulation of the argument __proto__ causes improperly controlled modification of object prototype attributes. Remote exploitation of the attack is possible. The exploit has been publicly disclosed and may be utilized. The code repository of the project has not been active for many years.
- How severe is CVE-2026-6621?
- CVE-2026-6621 has a CVSS 3.x base score of 7.3, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.
- Is CVE-2026-6621 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2026-6621?
- 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-2026-6621 have an EU (EUVD) identifier?
- Yes. CVE-2026-6621 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-23812.
- When was CVE-2026-6621 published?
- CVE-2026-6621 was published on 2026-04-20 and last updated on 2026-06-17.
References
- https://github.com/sudo-secure/security-research/blob/main/extend-deep/prototype-pollution/PoC.md
- https://vuldb.com/submit/792387
- https://vuldb.com/vuln/358256
- https://vuldb.com/vuln/358256/cti
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