CVE-2026-34520: AIOHTTP's C parser (llhttp) accepts null bytes and control characters in response header values - header injection/security bypass
(updated )
The C parser (the default for most installs) accepted null bytes and control characters in request headers.
References
- github.com/advisories/GHSA-63hf-3vf5-4wqf
- github.com/aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4
- github.com/aio-libs/aiohttp/releases/tag/v3.13.4
- github.com/aio-libs/aiohttp/security/advisories/GHSA-63hf-3vf5-4wqf
- github.com/pypa/advisory-database/tree/main/vulns/aiohttp/PYSEC-2026-2102.yaml
- nvd.nist.gov/vuln/detail/CVE-2026-34520
Code Behaviors & Features
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