blaze is a Scala library for building asynchronous pipelines, with a focus on network IO. Prior to 0.23.18 and from 1.0.0-M1 until 1.0.0-M42, five HTTP/1.1 conformance laxities in the hand-written Java parser under http/src/main/java/org/http4s/blaze/http/parser/ can cause blaze to derive a different request boundary than a stricter fronting intermediary. A default BlazeServerBuilder accepts invalid or valueless header field names that violate tchar syntax, obsolete folded field lines (obs-fold), unsupported Transfer-Encoding values, duplicate Content-Length fields, and requests containing both Transfer-Encoding and Content-Length. If a lenient or legacy proxy forwards the malformed bytes but interprets them differently, the disagreement can permit front-end authorization bypass, response-queue poisoning on pooled backend connections, or cache poisoning. Exploitation requires a pair of disagreeing parsers; no non-default blaze configuration is required. The affected checks are enforced in BodyAndHeaderParser and Http1ServerParser. This issue is fixed in versions 0.23.18 and 1.0.0-M42.
CVE-2026-73494
This high-severity CVE scores 7.4 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 69% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
- High severity, but no confirmed exploitation yet
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.4
- EG Score
- 7.4(medium)
- EG Risk
- 33(Track)EG Risk 33/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity74% × 45%Exploitation0% × 40%Automatability0% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 0%
- EPSS %ILE
- 31%
- KEV
- Not listed
Published
July 24, 2026
Last Modified
September 14, 2026
Advisory Details (9)
Auto-updated Sep 14, 2026v1.0.0-M42
Patch available: http4s/blaze v1.0.0-M42 (pre-release)
https://github.com/http4s/blaze/releases/tag/v1.0.0-M42v0.23.18
Patch available: http4s/blaze v0.23.18
https://github.com/http4s/blaze/releases/tag/v0.23.18commit e871ebb1d27f (http4s/blaze)
Patch available: http4s/blaze v0.23.18 (contains commit e871ebb1d27f)
https://github.com/http4s/blaze/commit/e871ebb1d27f50c98fd56988526ce42d0fee74d6commit c47d9675f876 (http4s/blaze)
Patch available: http4s/blaze v0.23.18 (contains commit c47d9675f876)
https://github.com/http4s/blaze/commit/c47d9675f87603f11b32a11d503626bdf9be5c7acommit a54bc9cd3175 (http4s/blaze)
Patch available: http4s/blaze v0.23.18 (contains commit a54bc9cd3175)
https://github.com/http4s/blaze/commit/a54bc9cd31758335c7f24e29763622fd03fcf734commit 927b67753a78 (http4s/blaze)
Patch available: http4s/blaze v0.23.18 (contains commit 927b67753a78)
https://github.com/http4s/blaze/commit/927b67753a78c13c4445dac9307f511f5c4878c3commit 4eec2007806a (http4s/blaze)
Patch available: http4s/blaze v0.23.18 (contains commit 4eec2007806a)
https://github.com/http4s/blaze/commit/4eec2007806aa9acfefb00ebb636ddc39a147a96commit 3f7c022e3066 (http4s/blaze)
Patch available: http4s/blaze v0.23.18 (contains commit 3f7c022e3066)
https://github.com/http4s/blaze/commit/3f7c022e306631b006dcb43a1d7f65c0d1966f17Multiple HTTP/1.1 request-smuggling primitives in blaze's Java wire parser · Advisory · http4s/blaze · GitHub
https://github.com/http4s/blaze/security/advisories/GHSA-mhvj-jhpq-885vVendor Advisories for CVE-2026-73494(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Affected Packages
(3 across 1 ecosystem)
Maven(3)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| org.http4s:blaze-http_2.13 | 1.0.0-M33 ... 1.0.0-M41 (9 versions) | 1.0.0-M42 | — |
| org.http4s:blaze-http_3 | 1.0.0-M33 ... 1.0.0-M41 (9 versions) | 1.0.0-M42 | — |
| org.http4s:http4s-blaze-server_2.13 | 0.10.0-M10 ... 0.23.9 (95 versions) | 0.23.18 | — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 10× in last 7d / 10× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-09-18 22:27 UTCEG score recompute
- 2026-09-18 19:28 UTCEPSS rescore
- 2026-09-18 02:56 UTCEG score recompute
- 2026-09-17 01:58 UTCEG score recompute
- 2026-09-16 14:08 UTCEPSS rescore
- 2026-09-16 06:38 UTCEG score recompute
- 2026-09-16 05:15 UTCEPSS rescore
- 2026-09-14 20:27 UTCEG score recompute
- 2026-09-14 20:16 UTCEG score recompute
- 2026-09-14 18:37 UTCEG score recompute
- 2026-08-12 21:21 UTCEG score recompute
Frequently asked(5)
What is CVE-2026-73494?
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Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-73494
Is Your Infrastructure Affected by CVE-2026-73494?
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