CVE-2026-73494
What it is
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.
At a glance
- Exploitability
- Can be exploited over the network without logging in. High risk of data exposure, data tampering.
- Exploit odds
- 0.6% chance of exploitation in the next 30 days (EPSS).
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- PublishedDisclosed publicly on CVE.org and NVD
- Last updatedMost recent change to the record
Why it ranks here
- Exploited in the wild: no, CISA does not list it.
- Exploit odds: 0.6% in the next 30 days (EPSS).
- Severity: 7.4 HIGH (CVSS).
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Exploit probability
- 0.6% · EPSS, next 30 days
- Weakness
- CWE-444
- Record status
- Deferred
Attack profile CVSS 3.1 · 7.4
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Raw vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Is it in your code?
Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.
Read https://cve-list.com/agent/cve/CVE-2026-73494.md and follow it. Check whether this project is affected by CVE-2026-73494. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
Fix and advisories
- https://github.com/http4s/blaze/commit/3f7c022e306631b006dcb43a1d7f65c0d1966f17
- https://github.com/http4s/blaze/commit/4eec2007806aa9acfefb00ebb636ddc39a147a96
- https://github.com/http4s/blaze/commit/927b67753a78c13c4445dac9307f511f5c4878c3
- https://github.com/http4s/blaze/commit/a54bc9cd31758335c7f24e29763622fd03fcf734
- https://github.com/http4s/blaze/commit/c47d9675f87603f11b32a11d503626bdf9be5c7a
- https://github.com/http4s/blaze/commit/e871ebb1d27f50c98fd56988526ce42d0fee74d6
- https://github.com/http4s/blaze/releases/tag/v0.23.18
- https://github.com/http4s/blaze/releases/tag/v1.0.0-M42
- https://github.com/http4s/blaze/security/advisories/GHSA-mhvj-jhpq-885v
References
- https://github.com/http4s/blaze/commit/3f7c022e306631b006dcb43a1d7f65c0d1966f17
- https://github.com/http4s/blaze/commit/4eec2007806aa9acfefb00ebb636ddc39a147a96
- https://github.com/http4s/blaze/commit/927b67753a78c13c4445dac9307f511f5c4878c3
- https://github.com/http4s/blaze/commit/a54bc9cd31758335c7f24e29763622fd03fcf734
- https://github.com/http4s/blaze/commit/c47d9675f87603f11b32a11d503626bdf9be5c7a
- https://github.com/http4s/blaze/commit/e871ebb1d27f50c98fd56988526ce42d0fee74d6
- https://github.com/http4s/blaze/releases/tag/v0.23.18
- https://github.com/http4s/blaze/releases/tag/v1.0.0-M42
- https://github.com/http4s/blaze/security/advisories/GHSA-mhvj-jhpq-885v