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Fencer Vulns
high 8.2

CVE-2023-35944 json

Envoy vulnerable to incorrect handling of HTTP requests and responses with mixed case schemes

published 2023-07-25 3 y ago modified 2026-09-10 59 d ago also BIT-envoy-2023-35944 , EUVD-2023-39928 , GHSA-pvgm-7jpg-pw5g

cvss
8.2
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 53%
public exploits
0
none known

Summary

Envoy is an open source edge and service proxy designed for cloud-native applications. Envoy allows mixed-case schemes in HTTP/2, however, some internal scheme checks are case-sensitive. Prior to versions 1.27.0, 1.26.4, 1.25.9, 1.24.10, and 1.23.12, this can lead to the rejection of requests with mixed-case schemes such as `htTp` or `htTps`, or the bypassing of some requests such as `https` in unencrypted connections. With a fix in versions 1.27.0, 1.26.4, 1.25.9, 1.24.10, and 1.23.12, Envoy will now lowercase scheme values by default, and change the internal scheme checks that were case-sensitive to be case-insensitive. There are no known workarounds for this issue.

Patch / fix

  • bitnami envoy 1.23.12, 1.24.10, 1.25.9, 1.26.4
  • envoyproxy envoy 1.23.12, 1.24.10, 1.25.9, 1.26.4

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-2023-35944 updated cvss 8.2

envoy: Incorrect handling of HTTP requests and responses with mixed case schemes

  • Red Hat RHOSSM 2.2 for RHEL 8 openshift-service-mesh/proxyv2-rhel8 2.2.10-3
    fixed: vendor fix RHSA-2023:5175
  • Red Hat RHOSSM 2.3 for RHEL 8 openshift-service-mesh/proxyv2-rhel8 2.3.6-4
    fixed: vendor fix RHSA-2023:4624
  • Red Hat RHOSSM 2.4 for RHEL 8 openshift-service-mesh/proxyv2-rhel8 2.4.2-7
    fixed: vendor fix RHSA-2023:4625
  • Red Hat RHOSSM 2.2 for RHEL 8 openshift-service-mesh/kiali-rhel8 1.48.8-1, openshift-service-mesh/pilot-rhel8 2.2.10-2, openshift-service-mesh/grafana-rhel8 2.2.10-1, openshift-service-mesh/istio-cni-rhel8 2.2.10-2, openshift-service-mesh/ratelimit-rhel8 2.2.10-1, openshift-service-mesh/prometheus-rhel8 2.2.10-1, +1 more Red Hat RHOSSM 2.3 for RHEL 8 openshift-service-mesh/pilot-rhel8 2.3.6-2, openshift-service-mesh/grafana-rhel8 2.3.6-1, openshift-service-mesh/istio-cni-rhel8 2.3.6-2, openshift-service-mesh/ratelimit-rhel8 2.3.6-1, openshift-service-mesh/prometheus-rhel8 2.3.6-1, openshift-service-mesh/istio-must-gather-rhel8 2.3.6-2 Red Hat RHOSSM 2.4 for RHEL 8 openshift-service-mesh/pilot-rhel8 2.4.2-8, openshift-service-mesh/grafana-rhel8 2.4.2-3, openshift-service-mesh/istio-cni-rhel8 2.4.2-8, openshift-service-mesh/ratelimit-rhel8 2.4.2-4, openshift-service-mesh/istio-rhel8-operator 2.4.2-8, openshift-service-mesh/istio-must-gather-rhel8 2.4.2-4
    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
total
Assessed
2 y ago

Exploit prediction

0.70% chance of exploitation in the next 30 days, higher than 53% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/envoyproxy/envoy/security/advisories/GHSA-pvgm-7jpg-pw5g referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
NVD 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
OSV 3.1 8.2 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

Affected packages

ecosystem package affected fixed in
bitnami envoy
>=1.23.0, <1.23.12
>=1.24.0, <1.24.10
>=1.25.0, <1.25.9
>=1.26.0, <1.26.4
1.23.12
1.24.10
1.25.9
1.26.4

Affected products

  • envoyproxy envoy

Classification

Weakness
  • CWE-20 Improper Input Validation
  • 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.