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CVE-2026-48743

Envoyproxy Envoy vulnerability

7.5 HIGHPublic exploitEPSS 0.30%
  1. Published26 Jun 2026

Description

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to 1.35.11, 1.36.7, 1.37.3, and 1.38.1, Envoy can translate a downstream HTTP/3 request that is complete at the transport layer (HEADERS with FIN / headers-only close) but still carries a nonzero Content-Length into a complete upstream HTTP/1 request with unresolved body debt. In an HTTP/1 upstream deployment where the origin replies before reading the declared body and keeps the connection reusable, the beginning of the next Envoy-generated upstream request can be consumed as the first request's body. The remaining bytes are then parsed by the origin as a new HTTP/1 request. This was reproduced as a route-bypass/desync: direct /pwn was denied by Envoy, but the second downstream H3 stream received the response for backend-parsed GET /pwn HTTP/1.1. This vulnerability is fixed in 1.35.11, 1.36.7, 1.37.3, and 1.38.1.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityHigh
Privileges requiredNone
User interactionNone
ScopeChanged
ConfidentialityLow
IntegrityHigh
AvailabilityNone
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N

Affected products

Envoyproxy Envoy≥ 1.35.0 < 1.35.13 · ≥ 1.36.0 < 1.36.9 · ≥ 1.37.0 < 1.37.5 · ≥ 1.38.0 < 1.38.3

Remediation

Fixed in
Envoyproxy Envoy≥ 1.35.13

References

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Frequently asked

Is CVE-2026-48743 being actively exploited?

CVE-2026-48743 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.30%.

How severe is CVE-2026-48743?

CVE-2026-48743 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.30% probability of exploitation.

Which products are affected by CVE-2026-48743?

Affected products include Envoyproxy Envoy.

How do I fix CVE-2026-48743?

Upgrade affected software to a fixed version, for example Envoyproxy Envoy 1.35.13 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-48743 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.