CVE-2026-34519
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, an attacker who controls the reason parameter when creating a Response may be able to inject extra headers or similar exploits. This issue has been patched in version 3.13.4.
02 / AFFECTED SOFTWARE
Affected packages
304 explicit affected versions
304 explicit affected versions
151 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, an attacker who controls the reason parameter when creating a Response may be able to inject extra headers or similar exploits. This issue has been patched in version 3.13.4.
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, an attacker who controls the reason parameter when creating a Response may be able to inject extra headers or similar exploits. This issue has been patched in version 3.13.4.
### Summary An attacker who controls the `reason` parameter when creating a `Response` may be able to inject extra headers or similar exploits. ### Impact In the unlikely situation that an application allows untrusted data to be used in the response's `reason` parameter, then an attacker could manipulate the response to send something different from what the developer intended. ----- Patch: https://github.com/aio-libs/aiohttp/commit/53b35a2f8869c37a133e60bf1a82a1c01642ba2b
05 / REFERENCES
Further evidence
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34519.json
- https://github.com/aio-libs/aiohttp/commit/53b35a2f8869c37a133e60bf1a82a1c01642ba2b
- https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4
- https://github.com/aio-libs/aiohttp/security/advisories/GHSA-mwh4-6h8g-pg8w
- https://nvd.nist.gov/vuln/detail/CVE-2026-34519
- https://github.com/aio-libs/aiohttp