How severe is CVE-2021-47664?

CVE-2021-47664 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2021-47664 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.

How do I fix CVE-2021-47664?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2021-47664 have an EU (EUVD) identifier?

Yes. CVE-2021-47664 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-12117.

When was CVE-2021-47664 published?

CVE-2021-47664 was published on 2025-04-24 and last updated on 2026-06-17.

CVE-2021-47664

CVE-2021-47664 is a medium-severity vulnerability with a CVSS 3.x base score of 5.3. 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-203.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
EPSS exploit prediction: 0% (27th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-12117
Weakness: CWE-203
Published: 2025-04-24
Last modified: 2026-06-17

Description

Due to improper authentication mechanism an unauthenticated remote attacker can enumerate valid usernames.

Frequently asked questions

What is CVE-2021-47664?: Due to improper authentication mechanism an unauthenticated remote attacker can enumerate valid usernames.
How severe is CVE-2021-47664?: CVE-2021-47664 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2021-47664 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.
How do I fix CVE-2021-47664?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2021-47664 have an EU (EUVD) identifier?: Yes. CVE-2021-47664 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-12117.
When was CVE-2021-47664 published?: CVE-2021-47664 was published on 2025-04-24 and last updated on 2026-06-17.

References

https://www.sciencedirect.com/science/article/pii/S2351978921001657

Other CWE-203 (Observable Discrepancy) vulnerabilities

CVE-2019-25337 — Critical (CVSS 9.8): OwnCloud 8.1.8 contains a username enumeration vulnerability that allows remote attackers to discover user accounts by…
CVE-2026-23519 — Critical (CVSS 9.8): RustCrypto CMOV provides conditional move CPU intrinsics which are guaranteed on major platforms to execute in…
CVE-2025-27667 — Critical (CVSS 9.8): Vasion Print (formerly PrinterLogic) before Virtual Appliance Host 22.0.843 Application 20.0.1923 allows Administrative…
CVE-2024-25714 — Critical (CVSS 9.8): In Rhonabwy through 1.1.13, HMAC signature verification uses a strcmp function that is vulnerable to side-channel…
CVE-2024-25191 — Critical (CVSS 9.8): php-jwt 1.0.0 uses strcmp (which is not constant time) to verify authentication, which makes it easier to bypass…
CVE-2024-25190 — Critical (CVSS 9.8): l8w8jwt 2.2.1 uses memcmp (which is not constant time) to verify authentication, which makes it easier to bypass…

Browse all CWE-203 (Observable Discrepancy) vulnerabilities →