How severe is CVE-2026-34525?

CVE-2026-34525 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.

Is CVE-2026-34525 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (21st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-34525?

CVE-2026-34525 affects Aiohttp. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-34525?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-34525 have an EU (EUVD) identifier?

Yes. CVE-2026-34525 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18048.

When was CVE-2026-34525 published?

CVE-2026-34525 was published on 2026-04-01 and last updated on 2026-06-17.

CVE-2026-34525

CVE-2026-34525 is a medium-severity vulnerability in Aiohttp with a CVSS 3.x base score of 5.3. 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-20.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
CVSS v4: 6.3
EPSS exploit prediction: 0% (21st percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-18048
Weakness: CWE-20
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, multiple Host headers were allowed in aiohttp. This issue has been patched in version 3.13.4.

Frequently asked questions

What is CVE-2026-34525?: AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, multiple Host headers were allowed in aiohttp. This issue has been patched in version 3.13.4.
How severe is CVE-2026-34525?: CVE-2026-34525 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability none.
Is CVE-2026-34525 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (21st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-34525?: CVE-2026-34525 affects Aiohttp. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-34525?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-34525 have an EU (EUVD) identifier?: Yes. CVE-2026-34525 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-18048.
When was CVE-2026-34525 published?: CVE-2026-34525 was published on 2026-04-01 and last updated on 2026-06-17.

References

Affected products (1)

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

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