Envoy through 1.15.0 only considers the first value when multiple header values are present for some HTTP headers.

published 2020-10-01 6 y ago modified 2026-09-08 2 mo ago also BIT-envoy-2020-25017 , EUVD-2020-17716 , GHSA-2v25-cjjq-5f4w

cvss: 8.3; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 1.3%; EPSS 1.3% chance of exploitation in 30 days, percentile 70%
public exploits: 0; none known

Envoy through 1.15.0 only considers the first value when multiple header values are present for some HTTP headers. Envoy’s setCopy() header map API does not replace all existing occurences of a non-inline header.

Patch / fix

fixed in 2 distros 1

bitnami envoy 1.12.7, 1.13.4, 1.14.4, 1.15.1
envoyproxy envoy 1.12.7, 1.13.4, 1.14.4, 1.15.1

servicemesh-proxy service mesh 1.1 1.1.9-1.el8

red hat advisories RHSA-2020:4129

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-2020-25017 updated 2025-11-21 cvss 8.3

envoyproxy/envoy: incorrectly handles multiple HTTP headers in requests

Red Hat OpenShift Service Mesh 1.1 servicemesh-proxy 1.1.9-1.el8
fixed: vendor fix RHSA-2020:4129

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

Exploit prediction

1.32% chance of exploitation in the next 30 days, higher than 70% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/envoyproxy/envoy/security/advisories/GHSA-2v25-cjjq-5f4w referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	8.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L
NVD	2.0	7.5	AV:N/AC:L/Au:N/C:P/I:P/A:P
OSV	3.1	8.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L

Affected packages

ecosystem	package	affected	fixed in
bitnami	envoy	<1.12.7 >=1.13.0, <1.13.4 >=1.14.0, <1.14.4 >=1.15.0, <1.15.1	1.12.7 1.13.4 1.14.4 1.15.1

References

github.com /envoyproxy/envoy/security/advisories/GHSA-2v25-cjjq-5f4w
exploit, third-party-advisory, advisory
groups.google.com /forum/#%21forum/envoy-security-announce
web
nvd.nist.gov /vuln/detail/CVE-2020-25017
web

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.

Summary