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TI-2023-12221 Aliases CVE-2023-27493

Envoy doesn't escape HTTP header values

Priority HIGH 74CWE-20Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
High · High · None
Fix status
Partial Red Hat: 1 fixed, 1 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat.

Summary

Envoy is an open source edge and service proxy designed for cloud-native applications. Prior to versions 1.26.0, 1.25.3, 1.24.4, 1.23.6, and 1.22.9, Envoy does not sanitize or escape request properties when generating request headers. This can lead to characters that are illegal in header values to be sent to the upstream service. In the worst case, it can cause upstream service to interpret the original request as two pipelined requests, possibly bypassing the intent of Envoy’s security policy. Versions 1.26.0, 1.25.3, 1.24.4, 1.23.6, and 1.22.9 contain a patch. As a workaround, disable adding request headers based on the downstream request properties, such as downstream certificate properties.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00507 43rd percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Partial envoy (envoyproxy): 1.25.3, 1.24.4, 1.23.6 +1Red Hat: 1 advisoryRed Hat: 1 fixed, 1 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
envoyproxyenvoy1.25.0 to before 1.25.3; 1.24.0 to before 1.24.4; 1.23.0 to before 1.23.6; before 1.22.91.25.3, 1.24.4, 1.23.6, 1.22.9Patch availableCNA
  • envoy Vendorenvoyproxy Affected 1.25.0 to before 1.25.3; 1.24.0 to before 1.24.4; 1.23.0 to before 1.23.6; before 1.22.9 Fixed in 1.25.3, 1.24.4, 1.23.6, 1.22.9 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:*before 1.22.9; 1.23.0 to before 1.23.6; 1.24.0 to before 1.24.4; 1.25.0 to before 1.25.3Vulnerableenvoyproxy
  • cpe:2.3:a:envoyproxy:envoy:*:*:*:*:*:*:*:* Versions before 1.22.9; 1.23.0 to before 1.23.6; 1.24.0 to before 1.24.4; 1.25.0 to before 1.25.3 Vulnerable ·envoyproxy

Remediation

  • Fix · CNA envoy (envoyproxy) Fixed in 1.25.3, 1.24.4, 1.23.6, 1.22.9

Red Hat 1 advisory

  • RHSA-2023:4623 Released 2023-08-11 · Red Hat rating Important
    Red Hat OpenShift Service Mesh 2.2.9 security update
    • RHOSSM 2.2 for RHEL 8 openshift-service-mesh/proxyv2-rhel8

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
OpenShift Service Mesh 2.1AffectedNo fix yet
RHOSSM 2.2 for RHEL 8Fixed RHSA-2023:4623
Not affected: 1 product
  • RHOSSM 2.2 for RHEL 8

Timeline

  1. 2026-10-02 Threatist record created from CVE-2023-27493

References

Exploit 1

  • TI-2026-79288 Out-of-bounds write in Google Brotli decoder KEVCVSS 4.0CRITICAL 9.2
  • TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
  • TI-2024-20001 HTTP/2: CPU exhaustion due to CONTINUATION frame flood CVSS 3.1HIGH 7.5
  • TI-2024-18524 HTTP/2: memory exhaustion due to CONTINUATION frame flood CVSS 3.1HIGH 7.5
  • TI-2023-12215 Envoy client may fake the header `x-envoy-original-path` CVSS 3.1CRITICAL 9.1
  • TI-2023-18002 Envoy vulnerable to OAuth2 credentials exploit with permanent validity CVSS 3.1CRITICAL 9.8
See all 126 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences