How severe is CVE-2021-4464?

CVE-2021-4464 has a CVSS 4.0 base score of 9.3, rated critical severity.

Is CVE-2021-4464 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2021-4464?

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

Does CVE-2021-4464 have an EU (EUVD) identifier?

Yes. CVE-2021-4464 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-34714.

When was CVE-2021-4464 published?

CVE-2021-4464 was published on 2025-11-12 and last updated on 2026-06-17.

CVE-2021-4464

CVE-2021-4464 is a critical-severity vulnerability with a CVSS 4.0 base score of 9.3. 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-121.

Key facts

Severity: Critical (CVSS 4.0 base score 9.3)
EPSS exploit prediction: 2% (76th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2021-34714
Weakness: CWE-121
Published: 2025-11-12
Last modified: 2026-06-17

Description

FiberHome AN5506-04-FA firmware versions up to and including RP2631 and HG6245D prior to RP2602 contain a stack-based buffer overflow, as the HTTP service ('webs') fails to enforce maximum lengths for Cookie header values. When a cookie longer than 511 bytes is processed, a stack buffer is overrun, leading to a crash or potential control of execution flow.

Frequently asked questions

What is CVE-2021-4464?: FiberHome AN5506-04-FA firmware versions up to and including RP2631 and HG6245D prior to RP2602 contain a stack-based buffer overflow, as the HTTP service ('webs') fails to enforce maximum lengths for Cookie header values. When a cookie longer than 511 bytes is processed, a stack buffer is overrun, leading to a crash or potential control of execution flow.
How severe is CVE-2021-4464?: CVE-2021-4464 has a CVSS 4.0 base score of 9.3, rated critical severity.
Is CVE-2021-4464 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2021-4464?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2021-4464 have an EU (EUVD) identifier?: Yes. CVE-2021-4464 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2021-34714.
When was CVE-2021-4464 published?: CVE-2021-4464 was published on 2025-11-12 and last updated on 2026-06-17.

References

Other CWE-121 (Stack-based Buffer Overflow) vulnerabilities

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CVE-2026-12485 — Critical (CVSS 10.0): GV-I/O Box 4E is a smart embedded device with 4 input and 4 relays output that can be controlled over Ethernet and…
CVE-2026-37541 — Critical (CVSS 10.0): Buffer overflow vulnerability in Open Vehicle Monitoring System 3 (OVMS3) 3.3.005. In canformat_gvret.cpp, the length…
CVE-2026-42996 — Critical (CVSS 10.0): JS8Call through 2.3.1 and JS8Call-improved before 3.0 have a stack-based buffer overflow via a radio transmission of…

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