Ansible: AIOHTTP's C parser (llhttp) accepts null bytes and control characters in response header values - header
Affects ansibleSource GCVE Database
Not known to be exploited · CVSS 2.7 Low : upgrade to 14.3.0 when convenient.
Data as of 30 Oct 2026, 07:30 UTC
- Patch
- Available – fixed in 14.3.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:UExploitation evidence
Disclosed: evidence found.
CVE published 1 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.
What to do
Upgrade ansible to 14.3.0.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Homebrewansiblepkg:brew/ansibleOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
### Summary The C parser (the default for most installs) accepted null bytes and control characters in request headers. ### Impact An attacker could send header values that are interpreted differently than expected due to the presence of control characters. For example, `request.url.origin()` may return a different value than the raw Host header, or what a reverse proxy interpreted it as., potentially resulting in some kind of security bypass. ----- Patch: https://github.com/aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4
References
- github.com/aio-libs/aiohttp/security/advisories/GHSA-63hf-3vf5-4wqf (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-34520 (opens in a new tab)
- github.com/aio-libs/aiohttp/commit/9370b9714a7a56003cacd31a9b4ae16eab109ba4 (opens in a new tab)
- github.com/aio-libs/aiohttp (opens in a new tab)
- github.com/aio-libs/aiohttp/releases/tag/v3.13.4 (opens in a new tab)
- github.com/pypa/advisory-database/tree/main/vulns/aiohttp/PYSEC-2026-2102.yaml (opens in a new tab)