How severe is CVE-2026-34516?

CVE-2026-34516 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-2026-34516 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (35th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-34516?

CVE-2026-34516 affects Aiohttp. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-34516?

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-2026-34516 have an EU (EUVD) identifier?

Yes. CVE-2026-34516 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18040.

When was CVE-2026-34516 published?

CVE-2026-34516 was published on 2026-04-01 and last updated on 2026-06-17.

CVE-2026-34516

CVE-2026-34516 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% (35th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-18040
Weakness: CWE-770
Affected product: Aiohttp
Published: 2026-04-01
Last modified: 2026-06-17

Description

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, a response with an excessive number of multipart headers may be allowed to use more memory than intended, potentially allowing a DoS vulnerability. This issue has been patched in version 3.13.4.

Frequently asked questions

What is CVE-2026-34516?: AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, a response with an excessive number of multipart headers may be allowed to use more memory than intended, potentially allowing a DoS vulnerability. This issue has been patched in version 3.13.4.
How severe is CVE-2026-34516?: CVE-2026-34516 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-2026-34516 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (35th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-34516?: CVE-2026-34516 affects Aiohttp. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-34516?: 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-2026-34516 have an EU (EUVD) identifier?: Yes. CVE-2026-34516 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18040.
When was CVE-2026-34516 published?: CVE-2026-34516 was published on 2026-04-01 and last updated on 2026-06-17.

References

Affected products (1)

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

More vulnerabilities in Aiohttp

CVE-2026-34520 — Critical (CVSS 9.1): AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, the C parser…
CVE-2026-54280 — High (CVSS 7.5): AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.1, payload resources are…
CVE-2026-54279 — High (CVSS 7.5): AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.1, host-only cookies that…
CVE-2026-54278 — High (CVSS 7.5): AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.1, during cleanup it is…
CVE-2026-54277 — High (CVSS 7.5): AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.1, it is possible to…
CVE-2026-54275 — High (CVSS 7.5): AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.1, the server_hostname…

All CVEs affecting Aiohttp →

Other CWE-770 (Allocation of Resources Without Limits or Throttling) vulnerabilities

CVE-2026-31283 — Critical (CVSS 9.8): In Totara LMS v19.1.5 and before, the forgot password API does not implement rate limiting for the target email…
CVE-2020-37067 — Critical (CVSS 9.8): Filetto 1.0 FTP server contains a denial of service vulnerability in the FEAT command processing that allows attackers…
CVE-2021-47875 — Critical (CVSS 9.8): GeoGebra CAS Calculator 6.0.631.0 contains a denial of service vulnerability that allows attackers to crash the…
CVE-2025-11832 — Critical (CVSS 9.8): Allocation of Resources Without Limits or Throttling vulnerability in Azure Access Technology BLU-IC2, Azure Access…
CVE-2024-44241 — Critical (CVSS 9.8): The issue was addressed with improved bounds checks. This issue is fixed in iOS 18.1 and iPadOS 18.1, macOS Sequoia…
CVE-2022-3439 — Critical (CVSS 9.8): Allocation of Resources Without Limits or Throttling in GitHub repository ikus060/rdiffweb prior to 2.5.0.

Browse all CWE-770 (Allocation of Resources Without Limits or Throttling) vulnerabilities →