CVE-2026-34519: CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') in aio-libs aiohttp
CVE-2026-34519 is a vulnerability in aiohttp versions prior to 3. 13. 4 where improper neutralization of CRLF sequences in HTTP headers can occur. Specifically, an attacker controlling the 'reason' parameter when creating a Response could inject extra headers or perform similar exploits. This issue has been addressed and patched in aiohttp version 3. 13. 4. The vulnerability has a low severity score of 2. 7 and no known exploits in the wild.
AI Analysis
Technical Summary
The vulnerability CVE-2026-34519 in aiohttp (an asynchronous HTTP client/server framework for Python) involves improper neutralization of CRLF sequences in HTTP headers (CWE-113). Prior to version 3.13.4, if an attacker controls the 'reason' parameter during Response creation, they may inject additional HTTP headers or perform related attacks. This flaw was fixed in version 3.13.4, mitigating the risk of HTTP response splitting or header injection.
Potential Impact
An attacker able to control the 'reason' parameter in aiohttp Response objects before version 3.13.4 could inject extra HTTP headers or manipulate the HTTP response structure. This could potentially lead to HTTP response splitting attacks. However, the CVSS score of 2.7 indicates the impact is low, and no known exploits have been reported in the wild.
Mitigation Recommendations
Upgrade aiohttp to version 3.13.4 or later, where this vulnerability has been patched. No other mitigation steps are indicated or necessary once the update is applied.
CVE-2026-34519: CWE-113: Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') in aio-libs aiohttp
Description
CVE-2026-34519 is a vulnerability in aiohttp versions prior to 3. 13. 4 where improper neutralization of CRLF sequences in HTTP headers can occur. Specifically, an attacker controlling the 'reason' parameter when creating a Response could inject extra headers or perform similar exploits. This issue has been addressed and patched in aiohttp version 3. 13. 4. The vulnerability has a low severity score of 2. 7 and no known exploits in the wild.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability CVE-2026-34519 in aiohttp (an asynchronous HTTP client/server framework for Python) involves improper neutralization of CRLF sequences in HTTP headers (CWE-113). Prior to version 3.13.4, if an attacker controls the 'reason' parameter during Response creation, they may inject additional HTTP headers or perform related attacks. This flaw was fixed in version 3.13.4, mitigating the risk of HTTP response splitting or header injection.
Potential Impact
An attacker able to control the 'reason' parameter in aiohttp Response objects before version 3.13.4 could inject extra HTTP headers or manipulate the HTTP response structure. This could potentially lead to HTTP response splitting attacks. However, the CVSS score of 2.7 indicates the impact is low, and no known exploits have been reported in the wild.
Mitigation Recommendations
Upgrade aiohttp to version 3.13.4 or later, where this vulnerability has been patched. No other mitigation steps are indicated or necessary once the update is applied.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-03-30T16:03:31.047Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 69cd85bee6bfc5ba1df9d43b
Added to database: 4/1/2026, 8:53:18 PM
Last enriched: 4/10/2026, 12:04:56 AM
Last updated: 5/21/2026, 7:12:03 PM
Views: 90
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