KEVWire

Security intelligence, with context.

Response snapshot Oct 29, 2026, 02:31 UTC

Back to the wire
Permalink
VulnerabilityCVE-2026-118657

Echo: HTTPS Redirect and HSTS Bypass via Unconditional Trust of Forwarded Scheme Headers

Context.Scheme() unconditionally trusts four client-controlled HTTP headers to determine the request scheme, with no mechanism to configure trusted sources. This allows a remote unauthenticated attacker to bypass HTTPS redirect enforcement and suppress HSTS headers.

Published Updated

At a glance

Exploited
Not known
Severity
5.9 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: 5.4.0; github.com/labstack/echo/v4: 4.16.0. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-2ffq-g2xg-c22p (opens a new tab)

What happened

Description

Context.Scheme() unconditionally trusts four client-controlled HTTP headers to determine the request scheme, with no mechanism to configure trusted sources. This allows a remote unauthenticated attacker to bypass HTTPS redirect enforcement and suppress HSTS headers.

The trusted headers (checked in this order of precedence): 1. X-Forwarded-Proto 2. X-Forwarded-Protocol 3. X-Forwarded-Ssl 4. X-Url-Scheme

Threat model

Continue reading

Scenario A — Directly exposed application (vulnerable by default): The Echo application listens on HTTP and is reachable directly by clients (no L7 proxy in front), or an attacker can bypass the proxy and reach the backend directly. In this case, the attacker has full control over all request headers. Sending X-Forwarded-Proto: https defeats the HTTPSRedirect middleware entirely — traffic stays on plaintext HTTP, enabling man-in-the-middle attacks.

This is the primary scenario. The application is vulnerable by default with no misconfiguration required — simply using e.Pre(middleware.HTTPSRedirect()) as documented is sufficient.

Scenario B — Behind L7 proxy with header sanitization (reduced risk): If the application is strictly behind a correctly configured L7 proxy that always overwrites X-Forwarded-Proto and there is no direct access to the backend, the practical risk is lower. However, this relies on perimeter controls external to the framework, not on the framework itself. As Echo's own IP-extraction documentation states: *"you must not trust HTTP headers unconditionally."*

Root cause

context.go, lines 161–181:

func (c *Context) Scheme() string {
 if c.IsTLS() {
 return "https"
 }
 if scheme := c.request.Header.Get(HeaderXForwardedProto); scheme != "" {
 return scheme
 }
 if scheme := c.request.Header.Get(HeaderXForwardedProtocol); scheme != "" {
 return scheme
 }
 if ssl := c.request.Header.Get(HeaderXForwardedSsl); ssl == "on" {
 return "https"
 }
 if scheme := c.request.Header.Get(HeaderXUrlScheme); scheme != "" {
 return scheme
 }
 return "http"
}

Two additional issues with this implementation:

1. No value validation. Scheme() returns any arbitrary string from the header, not just "http" or "https". This breaks the documented contract ("returns the HTTP protocol scheme, http or https") and causes unexpected behavior in middleware that uses the return value to construct URLs (e.g., WWWRedirect builds scheme + "://www." + host + uri).

2. Consumed by security-critical middleware. The return value is used directly by redirect middleware (middleware/redirect.go:136) and secure middleware (middleware/secure.go:125) for security enforcement decisions.

Affected components

| Component | File | Line(s) | Impact | |-----------|------|---------|--------| | Context.Scheme() | context.go | 161–181 | Returns attacker-controlled scheme | | HTTPSRedirect | middleware/redirect.go | 147–151 | HTTPS enforcement bypassed | | HTTPSWWWRedirect | middleware/redirect.go | 154–161 | HTTPS enforcement bypassed | | HTTPSNonWWWRedirect | middleware/redirect.

go | 163–170 | HTTPS enforcement bypassed | | WWWRedirect | middleware/redirect.go | 172–177 | URL constructed with arbitrary scheme | | NonWWWRedirect | middleware/redirect.go | 179–184 | URL constructed with arbitrary scheme | | Secure middleware (HSTS) | middleware/secure.go | 125 | HSTS header suppressed |

This is an unsafe-by-default API surface, not just misconfiguration

This behavior is not accidental — it is codified in the project's own test suite. For example, middleware/redirect_test.go (lines 29–34) explicitly asserts that X-Forwarded-Proto: https on an HTTP request results in 200 OK (no redirect):

{
 whenHost: "labstack.com",
 whenHeader: map[string][]string{echo.HeaderXForwardedProto: {"https"}},
 expectLocation: "",
 expectStatusCode: http.StatusOK,
},

Similarly, middleware/secure_test.go (lines 42–53) and context_test.go (lines 1104–1111) assert that scheme is derived from the header.

The problem is not that the framework *can* use forwarded headers — that is legitimate behind a trusted proxy. The problem is that there is no mechanism to control whether this trust is appropriate, unlike the existing IP header trust model. Scheme() always trusts the headers, making any middleware that depends on it unsafe-by-default.

Inconsistency with existing trust model

Echo already recognizes this class of header-trust vulnerability for IP addresses. The IPExtractor mechanism with TrustOption (TrustLoopback, TrustPrivateNet, TrustLinkLocal, TrustIPRange) was introduced specifically because:

> *"you must not trust HTTP headers unconditionally. Otherwise, you might give someone a chance of deceiving you. A security risk!"* > — ip.go, lines 20–21

> *"If you put no proxy (e.g., directly facing the internet), all you need to (and have to) see is IP address from network layer. Any HTTP header is untrustable because the clients have full control what headers to be set."* > — ip.go, lines 36–38

No equivalent mechanism exists for scheme detection. Scheme() unconditionally trusts all four forwarded headers with no configuration, opt-in, or documentation warning.

Note on proxies and the "3 additional headers"

A correctly configured nginx proxy_set_header X-Forwarded-Proto $scheme; overwrites X-Forwarded-Proto with the actual incoming scheme. When a proxy does this, X-Forwarded-Proto is trustworthy and the three fallback headers (X-Forwarded-Protocol, X-Forwarded-Ssl, X-Url-Scheme) are never reached because X-Forwarded-Proto takes precedence in Scheme().

The three additional headers become real attack vectors specifically when: - The proxy does not set X-Forwarded-Proto at all (common in default proxy configs), or - The application is directly exposed (Scenario A above).

In such cases, an attacker can bypass via any of the four header

Affected package ranges reported by GitHub: github.com/labstack/echo/v5: < 5.4.0 github.com/labstack/echo/v4: < 4.16.0

Scores and how they were measured

CVSS base severity

5.9

Version 3.1As of

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/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

Follow Go modules: RSS feedAll its recordsAsk your AI assistant

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-2ffq-g2xg-c22p (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-2ffq-g2xg-c22p, 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: HTTPS Redirect and HSTS Bypass via Unconditional Trust of Forwarded Scheme Headers (CVE-2026-118657). https://kevwire.com/record/CVE-2026-118657

MLA

"Echo: HTTPS Redirect and HSTS Bypass via Unconditional Trust of Forwarded Scheme Headers (CVE-2026-118657)." KEVWire, 28 Oct. 2026, kevwire.com/record/CVE-2026-118657.

Chicago

KEVWire. "Echo: HTTPS Redirect and HSTS Bypass via Unconditional Trust of Forwarded Scheme Headers (CVE-2026-118657)." Last modified October 28, 2026. https://kevwire.com/record/CVE-2026-118657.

Evidence summary (plain text)

Echo: HTTPS Redirect and HSTS Bypass via Unconditional Trust of Forwarded Scheme Headers (Oct 28, 2026).
Context.Scheme() unconditionally trusts four client-controlled HTTP headers to determine the request scheme, with no mechanism to configure trusted sources. This allows a remote unauthenticated attacker to bypass HTTPS redirect enforcement and suppress HSTS headers.

The trusted headers (checked in this order of precedence):
1. X-Forwarded-Proto
2. X-Forwarded-Protocol
3. X-Forwarded-Ssl
4.
CVSS 5.9 (version 3.1; evidence as of Oct 28, 2026; https://github.com/advisories/GHSA-2ffq-g2xg-c22p).
Sources:
GitHub-reviewed advisory GHSA-2ffq-g2xg-c22p: https://github.com/advisories/GHSA-2ffq-g2xg-c22p
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
Record ID: CVE-2026-118657.
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, 02:00 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.

Record JSON

Your account

Email alerts

Email alerts are coming as part of KEVWire Premium: join the waitlist. To follow your stack today, use its RSS feed, which honors your filters, or connect an AI agent through the API.

Suggest an improvement

Ideas, missing sources, corrections, and bugs are all welcome. No account needed. Suggestions are reviewed by a person before anything changes.

Record details

Record detail