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Fencer Vulns
high 7.5

CVE-2026-48743 json

Envoy: HTTP/3 to HTTP/1 request smuggling via headers-only request with nonzero Content-Length

published 2026-06-26 4 mo ago modified 2026-10-25 14 d ago also BIT-envoy-2026-48743 , EUVD-2026-39822 , GHSA-8phg-2h2q-jgxf

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 22%
public exploits
0
none known

Summary

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.

Patch / fix

  • bitnami envoy 1.35.11, 1.36.7, 1.37.3, 1.38.1
  • envoyproxy envoy 1.35.11, 1.36.7, 1.37.3, 1.38.1
  • istioctl openSUSE Tumbleweed 1.30.2-1.1

opensuse advisories openSUSE-SU-2026:11141-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-48743 updated cvss 7.5

envoy: Envoy: Request desynchronization allows security policy bypass via HTTP/3 to HTTP/1 translation

  • Red Hat OpenShift Service Mesh 2 openshift-service-mesh/proxyv2-rhel9
    affected: workaround, no fix planned “Will not fix”
  • Red Hat OpenShift Service Mesh 3.2 openshift-service-mesh/istio-proxyv2-rhel9 1784953743
    fixed: vendor fix RHSA-2026:49744
  • Red Hat OpenShift Service Mesh 3.3 openshift-service-mesh/istio-proxyv2-rhel9 1784908639
    fixed: vendor fix RHSA-2026:49765
  • Red Hat OpenShift Service Mesh 3.2 openshift-service-mesh/istio-cni-rhel9 1784921753, openshift-service-mesh/istio-pilot-rhel9 1784921772, openshift-service-mesh/istio-ztunnel-rhel9 1784922382, openshift-service-mesh/istio-rhel9-operator 1784918117, openshift-service-mesh/istio-must-gather-rhel9 1784839815, openshift-service-mesh/istio-sail-operator-bundle 1785036373 Red Hat OpenShift Service Mesh 3.3 openshift-service-mesh/istio-cni-rhel9 1784885810, openshift-service-mesh/istio-pilot-rhel9 1784885681, openshift-service-mesh/istio-ztunnel-rhel9 1784886337, openshift-service-mesh/istio-rhel9-operator 1785316150, openshift-service-mesh/istio-must-gather-rhel9 1784885505, openshift-service-mesh/istio-sail-operator-bundle 1785322241
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

0.30% chance of exploitation in the next 30 days, higher than 22% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/envoyproxy/envoy/security/advisories/GHSA-8phg-2h2q-jgxf referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N

Affected packages

ecosystem package affected fixed in
bitnami envoy
>=1.35.0, <1.35.11
>=1.36.0, <1.36.7
>=1.37.0, <1.37.3
>=1.38.0, <1.38.1
1.35.11
1.36.7
1.37.3
1.38.1

Affected products

  • envoyproxy envoy

Classification

Weakness
  • CWE-444 Inconsistent Interpretation of HTTP Requests

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.