# CVE-2026-85077: Sanic HTTP/1.1 response header injection vulnerability

Source: https://junglewise.ai/threats/cve-2026-85077-sanic-http-1-1-response-header-injection-vulnerability  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-17. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-85077 · Severity: high · CVSS 8.2 · Published 2026-09-17

Sanic is an open-source Python web server and framework used to build web applications. A vulnerability in Sanic's HTTP response handling allows attackers to inject carriage-return and line-feed characters into response headers, which can lead to cache poisoning, session fixation through injected cookies, or corruption of security headers. Applications that accept attacker-controlled data in response headers, file downloads, or cookie attributes are particularly at risk.

## Quick answers

**Is CVE-2026-85077 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-85077 being exploited in the wild.

**How severe is CVE-2026-85077?** High severity, with a CVSS score of 8.2, published 17 September 2026.

**Which products and versions are affected?** Sanic Sanic Prior to 24.12.1, and 25.12.0.

**Is there a fix for CVE-2026-85077?** A patch was published on 2026-05-31: Fix available in versions 24.12.1 and 25.12.1 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-85077 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-85077?** Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a header injection flaw in sanic/response/types.py where HTTP/1.1 response header names and values are serialized without validation to reject carriage-return (CR) and line-feed (LF) characters. This allows attackers to inject newline sequences that split HTTP responses and inject arbitrary headers. The attack vector is network-based and requires the application to place untrusted data in response.headers, file() filename parameters, or cookie path/domain attributes. Depending on intermediary proxies and application behavior, this enables session fixation, cache poisoning, and security header corruption. Patches are available in versions 24.12.1 and 25.12.1.

## Affected products

- Sanic Sanic Prior to 24.12.1, and 25.12.0

## Timeline

- 2026-09-17: disclosed: CVE-2026-85077 published
- 2026-05-31: patched: Fix available in versions 24.12.1 and 25.12.1

## References

- [https://github.com/sanic-org/sanic/commit/47349d689d65fa1907977ac100e867894aeafb22](https://github.com/sanic-org/sanic/commit/47349d689d65fa1907977ac100e867894aeafb22)
- [https://github.com/sanic-org/sanic/commit/9a95bb1c187558949606b915f5162c15f2db781b](https://github.com/sanic-org/sanic/commit/9a95bb1c187558949606b915f5162c15f2db781b)