How severe is CVE-2025-27421?

CVE-2025-27421 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2025-27421 being actively exploited?

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

How do I fix CVE-2025-27421?

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-2025-27421 have an EU (EUVD) identifier?

Yes. CVE-2025-27421 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-5565.

When was CVE-2025-27421 published?

CVE-2025-27421 was published on 2025-03-03 and last updated on 2026-06-17.

CVE-2025-27421

CVE-2025-27421 is a high-severity vulnerability with a CVSS 3.x base score of 7.5. 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-400.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (30th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-5565
Weakness: CWE-400
Published: 2025-03-03
Last modified: 2026-06-17

Description

Abacus is a highly scalable and stateless counting API. A critical goroutine leak vulnerability has been identified in the Abacus server's Server-Sent Events (SSE) implementation. The issue occurs when clients disconnect from the /stream endpoint, as the server fails to properly clean up resources and terminate associated goroutines. This leads to resource exhaustion where the server continues running but eventually stops accepting new SSE connections while maintaining high memory usage. The vulnerability specifically involves improper channel cleanup in the event handling mechanism, causing goroutines to remain blocked indefinitely. This vulnerability is fixed in 1.4.0.

Frequently asked questions

What is CVE-2025-27421?: Abacus is a highly scalable and stateless counting API. A critical goroutine leak vulnerability has been identified in the Abacus server's Server-Sent Events (SSE) implementation. The issue occurs when clients disconnect from the /stream endpoint, as the server fails to properly clean up resources and terminate associated goroutines. This leads to resource exhaustion where the server continues running but eventually stops accepting new SSE connections while maintaining high memory usage. The vulnerability specifically involves improper channel cleanup in the event handling mechanism, causing goroutines to remain blocked indefinitely. This vulnerability is fixed in 1.4.0.
How severe is CVE-2025-27421?: CVE-2025-27421 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2025-27421 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (30th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2025-27421?: 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-2025-27421 have an EU (EUVD) identifier?: Yes. CVE-2025-27421 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-5565.
When was CVE-2025-27421 published?: CVE-2025-27421 was published on 2025-03-03 and last updated on 2026-06-17.

References

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