CVE-2024-23326

Envoy incorrectly accepts HTTP 200 response for entering upgrade mode

HIGH

8.2

CVSS Score

Published: June 4, 2024 at 08:05 PM UTC

Updated: June 17, 2026 at 07:12 AM UTC

1 product affected across 1 vendorEnvoy

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Severity

HIGH8.2

Exploit prediction

EPSS 0.4%

SSVC

No known exploit

Description

Envoy is a cloud-native, open source edge and service proxy. A theoretical request smuggling vulnerability exists through Envoy if a server can be tricked into adding an upgrade header into a response. Per RFC https://www.rfc-editor.org/rfc/rfc7230#section-6.7 a server sends 101 when switching protocols. Envoy incorrectly accepts a 200 response from a server when requesting a protocol upgrade, but 200 does not indicate protocol switch. This opens up the possibility of request smuggling through Envoy if the server can be tricked into adding the upgrade header to the response.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Envoy · Envoyproxy

95%

v ≤ 1.28.3v ≤ 1.29.4v ≤ 1.30.1v < 1.27.61.28.0 ≤ v < 1.28.41.29.0 ≤ v < 1.29.51.30.0 ≤ v < 1.30.2<= 1.27.5

Affected range stops below 1.27.6, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.28.4, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.29.5, so it looks safe — our inference, not a vendor statement

Affected range stops below 1.30.2, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

https://github.com/envoyproxy/envoy/security/advisories/GHSA-vcf8-7238-v74c

References (1)

x_refsource_CONFIRMVendor Advisory

Source: [email protected]

https://github.com/envoyproxy/envoy/security/advisories/GHSA-vcf8-7238-v74c

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

8.2HIGH[email protected]

Attack Vector: NETWORK
Complexity: LOW
Privileges: NONE
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: HIGH
Integrity: LOW
Availability: NONE

Vector?

Quick Info

StatusMODIFIED

CWE

CWE-391CWE-444

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