How severe is GHSA-c427-h43c-vf67?

No CVSS score has been assigned to GHSA-c427-h43c-vf67 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-c427-h43c-vf67?

GHSA-c427-h43c-vf67 affects the following packages: aiohttp (PyPI). Ecosystems affected: PyPI.

How do I fix GHSA-c427-h43c-vf67?

Update aiohttp to 3.13.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-c427-h43c-vf67 is resolved across your whole dependency graph.

How do I detect GHSA-c427-h43c-vf67 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for aiohttp. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-c427-h43c-vf67 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-c427-h43c-vf67?

O3 pinpoints whether GHSA-c427-h43c-vf67 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-c427-h43c-vf67 actively exploited in the wild?

No public exploit code has been indexed for GHSA-c427-h43c-vf67 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What type of vulnerability is GHSA-c427-h43c-vf67?

GHSA-c427-h43c-vf67 is classified as Improper Input Validation (CWE-20), CWE-444 (CWE-444). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-c427-h43c-vf67 published, and has it been updated?

GHSA-c427-h43c-vf67 was published on April 1, 2026 and was last updated on July 13, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

GHSA-c427-h43c-vf67

GHSA-c427-h43c-vf67 is a Improper Input Validation vulnerability in aiohttp. O3 Security confirms whether GHSA-c427-h43c-vf67 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

AIOHTTP accepts duplicate Host headers

Also known asCVE-2026-34525PYSEC-2026-2103

Published

Apr 1, 2026

Updated

Jul 13, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Blast Radius

1 pkg affected

🐍aiohttp

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Summary

Multiple Host headers were allowed in aiohttp.

Impact

Mostly this doesn't affect aiohttp security itself, but if a reverse proxy is applying security rules depending on the target Host, it is theoretically possible that the proxy and aiohttp could process different host names, possibly resulting in bypassing a security check on the proxy and getting a request processed by aiohttp in a privileged sub app when using Application.add_domain().

Patch: https://github.com/aio-libs/aiohttp/commit/e00ca3cca92c465c7913c4beb763a72da9ed8349 Patch: https://github.com/aio-libs/aiohttp/commit/53e2e6fc58b89c6185be7820bd2c9f40216b3000

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`aiohttp`	all versions	3.13.4

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for aiohttp. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update aiohttp to 3.13.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-c427-h43c-vf67 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-c427-h43c-vf67 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-c427-h43c-vf67. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Summary Multiple Host headers were allowed in aiohttp. ### Impact Mostly this doesn't affect aiohttp security itself, but if a reverse proxy is applying security rules depending on the target Host, it is theoretically possible that the proxy and aiohttp could process different host names, possibly resulting in bypassing a security check on the proxy and getting a request processed by aiohttp in a privileged sub app when using `Application.add_domain()`. ----- Patch: https://github.com/aio-libs/aiohttp/commit/e00ca3cca92c465c7913c4beb763a72da9ed8349 Patch: https://github.com/aio-libs/a

O3 Security · Impact-Aware SCA

Is GHSA-c427-h43c-vf67 in your dependencies?

O3 detects GHSA-c427-h43c-vf67 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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