CVE-2026-34525

MEDIUMNVD 5.35.3—

5.3

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.

CVSS v3: 5.3
EG Score: 5.3(medium)
EPSS: 32.1%
KEV: Not listed

Published

April 1, 2026

Last Modified

April 16, 2026

References (4)

security-advisories@githubhttps://github.com/aio-libs/aiohttp/commit/53e2e6fc58b89c6185be7820bd2c9f40216b3000
security-advisories@githubhttps://github.com/aio-libs/aiohttp/commit/e00ca3cca92c465c7913c4beb763a72da9ed8349
security-advisories@githubhttps://github.com/aio-libs/aiohttp/releases/tag/v3.13.4
security-advisories@githubhttps://github.com/aio-libs/aiohttp/security/advisories/GHSA-c427-h43c-vf67

Affected Packages

(1 across 1 ecosystem)

PyPI(1)

Package	Vulnerable range	Fixed in	Dependents
aiohttp	0.1 ... 3.9.5 (304 versions)	3.13.4	—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 16× in last 7d / 20× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-05-31 22:30 UTCepss_batch
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2026-05-31 00:16 UTCepss_batch
2026-05-31 00:16 UTCepss_batch
2026-05-31 00:16 UTCepss_batch
2026-05-29 13:44 UTCepss_batch
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2026-05-28 13:44 UTCepss_batch
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2026-05-27 13:40 UTCepss_batch
2026-05-27 13:40 UTCepss_batch
2026-05-27 13:40 UTCepss_batch
2026-05-26 13:44 UTCepss_batch
2026-05-26 07:18 UTCepss_batch
2026-05-26 07:18 UTCepss_batch
2026-05-23 00:08 UTCEG score recompute
2026-05-20 22:38 UTCepss_batch
2026-05-20 22:38 UTCepss_batch
2026-05-20 19:33 UTCEG score recompute

Frequently asked(5)

What is CVE-2026-34525?

CVE-2026-34525 is a medium vulnerability published on April 1, 2026. 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.

When was CVE-2026-34525 disclosed?

CVE-2026-34525 was first published in the National Vulnerability Database on April 1, 2026, with the most recent update on April 16, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2026-34525 actively exploited?

CVE-2026-34525 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 32.1% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2026-34525?

CVE-2026-34525 has a CVSS v3 base score of 5.3 (NVD).

How do I remediate CVE-2026-34525?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-34525, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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CVE-2026-34525

📅 Published

🔄 Last Modified

🔗 References (4)

Affected Packages

Weakness Classification(2)

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2026-34525?

🔗 Related CVEs(same CWE)

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Published

Last Modified

References (4)

Frequently asked(5)

Related CVEs(same CWE)