---
title: "CVE-2026-73494: Blaze - Authorization Bypass & Cache Poisoning"
description: "Blaze Scala library < 0.23.18 and 1.0.0-M1 to < 1.0.0-M42 contains an HTTP/1.1 parsing vulnerability caused by lax header and request boundary validation in Http1ServerParser, letting attackers cause authorization bypass or cache poisoning, exploit requires a pair of disagreeing parsers."
url: https://panop.io/threat-heartbeat/CVE-2026-73494/
---

# CVE-2026-73494 Blaze - Authorization Bypass & Cache Poisoning

Blaze Scala library < 0.23.18 and 1.0.0-M1 to < 1.0.0-M42 contains an HTTP/1.1 parsing vulnerability caused by lax header and request boundary validation in Http1ServerParser, letting attackers cause authorization bypass or cache poisoning, exploit requires a pair of disagreeing parsers.

CVSS base score 7.4 /10

High

CISA KEV

Not listed

Public exploit

None known

EPSS

0.63% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-73494)

## Details

Type

Authorization Bypass

Impact

Broken Access Control, Data Tampering

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Published

14 September 2026

Updated

15 October 2026

Weakness

[CWE-444](https://cwe.mitre.org/data/definitions/444.html)

## Vendor fix

Update to versions 0.23.18 or 1.0.0-M42 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-73494](https://nvd.nist.gov/vuln/detail/CVE-2026-73494)
- [https://github.com/http4s/blaze/commit/3f7c022e306631b006dcb43a1d7f65c0d1966f17](https://github.com/http4s/blaze/commit/3f7c022e306631b006dcb43a1d7f65c0d1966f17)
- [https://github.com/http4s/blaze/commit/4eec2007806aa9acfefb00ebb636ddc39a147a96](https://github.com/http4s/blaze/commit/4eec2007806aa9acfefb00ebb636ddc39a147a96)
- [https://github.com/http4s/blaze/commit/a54bc9cd31758335c7f24e29763622fd03fcf734](https://github.com/http4s/blaze/commit/a54bc9cd31758335c7f24e29763622fd03fcf734)
- [https://github.com/http4s/blaze/commit/c47d9675f87603f11b32a11d503626bdf9be5c7a](https://github.com/http4s/blaze/commit/c47d9675f87603f11b32a11d503626bdf9be5c7a)
- [https://github.com/http4s/blaze/commit/e871ebb1d27f50c98fd56988526ce42d0fee74d6](https://github.com/http4s/blaze/commit/e871ebb1d27f50c98fd56988526ce42d0fee74d6)
- [https://github.com/http4s/blaze/releases/tag/v0.23.18](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/releases/tag/v1.0.0-M42)
- [https://github.com/http4s/blaze/security/advisories/GHSA-mhvj-jhpq-885v](https://github.com/http4s/blaze/security/advisories/GHSA-mhvj-jhpq-885v)
- [https://github.com/http4s/blaze/commit/927b67753a78c13c4445dac9307f511f5c4878c3](https://github.com/http4s/blaze/commit/927b67753a78c13c4445dac9307f511f5c4878c3)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

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