How severe is CVE-2026-54277?

CVE-2026-54277 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-2026-54277 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (25th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-54277?

CVE-2026-54277 affects Aiohttp. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-54277?

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-2026-54277 have an EU (EUVD) identifier?

Yes. CVE-2026-54277 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38314.

When was CVE-2026-54277 published?

CVE-2026-54277 was published on 2026-06-22 and last updated on 2026-06-30.

CVE-2026-54277

CVE-2026-54277 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-770.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v4: 6.6
EPSS exploit prediction: 0% (25th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-38314
Weakness: CWE-770
Affected product: Aiohttp
Published: 2026-06-22
Last modified: 2026-06-30

Description

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.1, it is possible to bypass the max_line_size check in parts of an HTTP request in the C parser. If using the optimised C parser (the default in pre-built wheels), then an attacker may be able to send oversized lines through the HTTP parser and use an excessive amount of memory, potentially leading to DoS. This vulnerability is fixed in 3.14.1.

Frequently asked questions

What is CVE-2026-54277?: AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.1, it is possible to bypass the max_line_size check in parts of an HTTP request in the C parser. If using the optimised C parser (the default in pre-built wheels), then an attacker may be able to send oversized lines through the HTTP parser and use an excessive amount of memory, potentially leading to DoS. This vulnerability is fixed in 3.14.1.
How severe is CVE-2026-54277?: CVE-2026-54277 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-2026-54277 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (25th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-54277?: CVE-2026-54277 affects Aiohttp. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-54277?: 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-2026-54277 have an EU (EUVD) identifier?: Yes. CVE-2026-54277 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-38314.
When was CVE-2026-54277 published?: CVE-2026-54277 was published on 2026-06-22 and last updated on 2026-06-30.

References

Affected products (1)

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

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