How severe is GHSA-46q4-43ph-c6fr?

GHSA-46q4-43ph-c6fr has a CVSS score of 7.4/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by GHSA-46q4-43ph-c6fr?

GHSA-46q4-43ph-c6fr affects the following packages: org.http4s:blaze-http_2.13 (Maven), org.http4s:blaze-http_2.12 (Maven), org.http4s:blaze-http_3 (Maven), org.http4s:blaze-http_3 (Maven), org.http4s:blaze-http_2.13 (Maven). Ecosystems affected: Maven.

How do I fix GHSA-46q4-43ph-c6fr?

Update org.http4s:blaze-http_2.13 to 0.23.18 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-46q4-43ph-c6fr is resolved across your whole dependency graph.

How do I detect GHSA-46q4-43ph-c6fr in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.http4s:blaze-http_2.13, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-46q4-43ph-c6fr if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is GHSA-46q4-43ph-c6fr actively exploited in the wild?

No public exploit code has been indexed for GHSA-46q4-43ph-c6fr yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-46q4-43ph-c6fr?

GHSA-46q4-43ph-c6fr has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 39th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-46q4-43ph-c6fr?

GHSA-46q4-43ph-c6fr is classified as CWE-444 (CWE-444). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-46q4-43ph-c6fr published, and has it been updated?

GHSA-46q4-43ph-c6fr was published on July 24, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

HIGH severity

GHSA-46q4-43ph-c6fr — blaze-http_2.13

HIGHFix: http4s/blaze@ef3e666

GHSA-46q4-43ph-c6fr is a high-severity (CVSS 7.4) CWE-444 vulnerability in org.http4s:blaze-http_2.13. A fix is available for org.http4s:blaze-http_2.13 — see the affected versions and patch details below.

blaze: Chunked-body trailer fields promoted into Request.headers in blaze-server (front-end header-sanitization bypass)

Also known asCVE-2026-73495

Published

Jul 24, 2026

Updated

Aug 12, 2026

Affected

5 pkgs

Patched

5 / 5

Exploits

None indexed

Exploitation data as of Sep 26, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-46q4-43ph-c6fr.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs39th percentile — riskier than 39% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-46q4-43ph-c6fr by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

5 pkgs affected

☕org.http4s:blaze-http_2.13☕org.http4s:blaze-http_2.12☕org.http4s:blaze-http_3☕org.http4s:blaze-http_3☕org.http4s:blaze-http_2.13

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Summary

blaze-server can merge HTTP/1.1 chunked-body trailer fields into Request.headers. Because trailer fields are attacker-controlled, an unauthenticated remote client can inject arbitrary header names/values (e.g. X-Forwarded-For, internal-auth headers) that a fronting proxy sanitized from the request-header section, bypassing header-based trust decisions in the application.

Impact

Any http4s application using BlazeServerBuilder over HTTP/1.1 whose routes or middleware trust proxy-set headers (e.g., X-Forwarded-For, X-Real-IP, X-Forwarded-Host, org-internal auth headers) is affected. Where a fronting proxy strips/normalizes those headers but forwards chunked bodies with trailers intact, an attacker can spoof client IP for allow-lists/rate-limits/audit, forge the https scheme, or inject internal-auth headers. A promoted Connection: close trailer is also honored, allowing attacker-controlled termination of pooled backend connections.

Workarounds

Deploy behind a proxy that removes trailer fields (or rejects requests that use trailers) before forwarding; until patched, avoid trust decisions based on headers that a proxy is relied upon to sanitize.

Affected Packages

5 total 5 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.http4s:blaze-http_2.13`	all versions	0.23.18`org.http4s:blaze-http_2.13:0.23.18`
☕Maven	`org.http4s:blaze-http_2.12`	all versions	0.23.18`org.http4s:blaze-http_2.12:0.23.18`
☕Maven	`org.http4s:blaze-http_3`	all versions	0.23.18`org.http4s:blaze-http_3:0.23.18`
☕Maven	`org.http4s:blaze-http_3`	≥ 1.0.0-M1&&< 1.0.0-M42	1.0.0-M42`org.http4s:blaze-http_3:1.0.0-M42`
☕Maven	`org.http4s:blaze-http_2.13`	≥ 1.0.0-M1&&< 1.0.0-M42	1.0.0-M42`org.http4s:blaze-http_2.13:1.0.0-M42`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.http4s:blaze-http_2.13, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.http4s:blaze-http_2.13 to 0.23.18 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-46q4-43ph-c6fr is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### Summary blaze-server can merge HTTP/1.1 chunked-body trailer fields into `Request.headers`. Because trailer fields are attacker-controlled, an unauthenticated remote client can inject arbitrary header names/values (e.g. `X-Forwarded-For`, internal-auth headers) that a fronting proxy sanitized from the request-header section, bypassing header-based trust decisions in the application. ### Impact Any http4s application using `BlazeServerBuilder` over HTTP/1.1 whose routes or middleware trust proxy-set headers (e.g., `X-Forwarded-For`, `X-Real-IP`, `X-Forwarded-Host`, org-internal auth