Org.http4s:http4s blaze server 2.13: blaze: Multiple HTTP/1.1 request-smuggling primitives in blaze's Java wire parser
Multiple HTTP/1.1 request-smuggling vulnerabilities exist in the blaze server's Java wire parser used by org.http4s:http4s-blaze-server_2.13. These parser laxities cause disagreement on request boundaries when paired with stricter intermediaries, potentially allowing bypass of front-end access controls, response queue poisoning, and cache poisoning. The vulnerabilities affect versions prior to 0.23.18. Exploitability depends on the presence of a fronting proxy that interprets requests differently. Deploying behind an RFC-compliant reverse proxy can mitigate the risk until an upgrade is possible.
AI Analysis
Technical Summary
The blaze server component of org.http4s:http4s-blaze-server_2.13 contains five independent HTTP/1.1 conformance laxities in its hand-written Java parser, leading to request-boundary disagreements with stricter intermediaries. These disagreements can be exploited when a fronting proxy forwards malformed bytes but derives different message boundaries, enabling HTTP request smuggling attacks. Such attacks can result in front-end ACL or authentication bypass, response queue poisoning on pooled backend connections, and cache poisoning. The vulnerabilities are reachable with default BlazeServerBuilder configurations and affect all versions before 0.23.18.
Potential Impact
If exploited, these vulnerabilities can allow attackers to bypass access controls or authentication mechanisms at the front end, poison response queues on backend connections, and poison caches. The actual impact depends on the fronting proxy's behavior and its strictness in parsing HTTP requests. The risk is higher when lenient or legacy intermediaries are used as proxies.
Mitigation Recommendations
A fix is available in versions 0.23.18 and later. Until upgrading, it is recommended to deploy the blaze server behind an RFC-compliant reverse proxy such as nginx, HAProxy, Envoy, or AWS ALB that rejects or re-serializes malformed HTTP requests at the edge. This approach neutralizes most of the vulnerabilities for deployments that cannot upgrade immediately.
Org.http4s:http4s blaze server 2.13: blaze: Multiple HTTP/1.1 request-smuggling primitives in blaze's Java wire parser
Description
Multiple HTTP/1.1 request-smuggling vulnerabilities exist in the blaze server's Java wire parser used by org.http4s:http4s-blaze-server_2.13. These parser laxities cause disagreement on request boundaries when paired with stricter intermediaries, potentially allowing bypass of front-end access controls, response queue poisoning, and cache poisoning. The vulnerabilities affect versions prior to 0.23.18. Exploitability depends on the presence of a fronting proxy that interprets requests differently. Deploying behind an RFC-compliant reverse proxy can mitigate the risk until an upgrade is possible.
CVSS v3.1
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The blaze server component of org.http4s:http4s-blaze-server_2.13 contains five independent HTTP/1.1 conformance laxities in its hand-written Java parser, leading to request-boundary disagreements with stricter intermediaries. These disagreements can be exploited when a fronting proxy forwards malformed bytes but derives different message boundaries, enabling HTTP request smuggling attacks. Such attacks can result in front-end ACL or authentication bypass, response queue poisoning on pooled backend connections, and cache poisoning. The vulnerabilities are reachable with default BlazeServerBuilder configurations and affect all versions before 0.23.18.
Potential Impact
If exploited, these vulnerabilities can allow attackers to bypass access controls or authentication mechanisms at the front end, poison response queues on backend connections, and poison caches. The actual impact depends on the fronting proxy's behavior and its strictness in parsing HTTP requests. The risk is higher when lenient or legacy intermediaries are used as proxies.
Mitigation Recommendations
A fix is available in versions 0.23.18 and later. Until upgrading, it is recommended to deploy the blaze server behind an RFC-compliant reverse proxy such as nginx, HAProxy, Envoy, or AWS ALB that rejects or re-serializes malformed HTTP requests at the edge. This approach neutralizes most of the vulnerabilities for deployments that cannot upgrade immediately.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-mhvj-jhpq-885v
- Osv Schema Version
- 1.4.0
- Aliases
- []
- Ecosystems
- ["Maven"]
- Database Specific Severity
- HIGH
- Cvss Version
- 3.1
Threat ID: 6a65421d9c2644c7f808808d
Added to database: 07/25/2026, 23:09:17 UTC
Last enriched: 07/25/2026, 23:50:45 UTC
Last updated: 07/26/2026, 03:46:30 UTC
Views: 4
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