DirectorySecurity AdvisoriesPricing
/
Sign in
Security Advisories

CVE-2025-43859

NVD

https://nvd.nist.gov/vuln/detail/CVE-2025-43859

Severity

9.1

Critical

CVSS V3

Eliminate CVEs with Chainguard hardened images

Build, ship, and run secure software with minimal, hardened container images — rebuilt from source daily and guarded under our industry-leading remediation SLA.

Start for free

Summary

h11 accepts some malformed Chunked-Encoding bodies

Description

h11 is a Python implementation of HTTP/1.1. Prior to version 0.16.0, a leniency in h11's parsing of line terminators in chunked-coding message bodies can lead to request smuggling vulnerabilities under certain conditions. This issue has been patched in version 0.16.0. Since exploitation requires the combination of buggy h11 with a buggy (reverse) proxy, fixing either component is sufficient to mitigate this issue.

References

Affected packages

The trusted source for open source

Talk to an expert
PrivacyTerms

Product

Chainguard ContainersChainguard LibrariesChainguard VMsIntegrationsPricing

Solutions

FedRAMPPCI DSSCMMC 2.0Golden ImagesCVE RemediationPublic Sector

Customers

Customer StoriesChainguard Reviews

Resources

Events & WebinarsSupply Chain Security 101Chainguard CoursesDocumentationTrust CenterChainguard Slack Community

Company

About UsBlogPartnersNewsroomCareersLegal
© 2026 Chainguard, Inc. All Rights Reserved.
Chainguard® and the Chainguard logo are registered trademarks of Chainguard, Inc. in the United States and/or other countries.
The other respective trademarks mentioned on this page are owned by the respective companies and use of them does not imply any affiliation or endorsement.