How severe is CVE-2026-54275?

CVE-2026-54275 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-2026-54275 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-54275?

CVE-2026-54275 affects Aiohttp. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-54275?

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-2026-54275 have an EU (EUVD) identifier?

Yes. CVE-2026-54275 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38312.

When was CVE-2026-54275 published?

CVE-2026-54275 was published on 2026-06-22 and last updated on 2026-06-26.

CVE-2026-54275

CVE-2026-54275 is a high-severity vulnerability in Aiohttp 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-297.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v4: 2.7
EPSS exploit prediction: 0% (18th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-38312
Weakness: CWE-297
Affected product: Aiohttp
Published: 2026-06-22
Last modified: 2026-06-26

Description

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.1, the server_hostname TLS SNI check can be bypassed when an existing connection is reused. If an application makes multiple requests to the same domain, but with different per-request server_hostname parameters, then the later calls may succeed by reusing the existing connection when they should have been rejected due to the TLS SNI check. This vulnerability is fixed in 3.14.1.

Frequently asked questions

What is CVE-2026-54275?: AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.1, the server_hostname TLS SNI check can be bypassed when an existing connection is reused. If an application makes multiple requests to the same domain, but with different per-request server_hostname parameters, then the later calls may succeed by reusing the existing connection when they should have been rejected due to the TLS SNI check. This vulnerability is fixed in 3.14.1.
How severe is CVE-2026-54275?: CVE-2026-54275 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-2026-54275 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-54275?: CVE-2026-54275 affects Aiohttp. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-54275?: 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-2026-54275 have an EU (EUVD) identifier?: Yes. CVE-2026-54275 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38312.
When was CVE-2026-54275 published?: CVE-2026-54275 was published on 2026-06-22 and last updated on 2026-06-26.

References

https://github.com/aio-libs/aiohttp/security/advisories/GHSA-4m7w-qmgq-4wj5

Affected products (1)

cpe:2.3:a:aiohttp:aiohttp:*:*:*:*:*:*:*:*

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