Summary
commit: e0f8d9b2047af417d8faf354b675941f3dac9891 (as-of 2026-02-04)
channel: GitHub security advisory (per SECURITY.md)
The local caddy admin API (default listen 127.0.0.1:2019) exposes a state-changing POST /load endpoint that replaces the entire running configuration.
When origin enforcement is not enabled (enforce_origin not configured), the admin endpoint accepts cross-origin requests (e.g., from attacker-controlled web content in a victim browser) and applies an attacker-supplied JSON config. this can change the admin listener settings and alter HTTP server behavior without user intent.
Severity
Medium
Justification:
- The attacker can apply an arbitrary caddy config (integrity impact) by driving a victim’s local admin API.
- Exploitation requires a victim running caddy with the admin API enabled and visiting an attacker-controlled page (or otherwise issuing the request from an untrusted local client).
Affected component
caddyconfig/load.go: adminLoad.handleLoad(/loadadmin endpoint)- Pinned callsite: https://github.com/caddyserver/caddy/blob/e0f8d9b2047af417d8faf354b675941f3dac9891/caddyconfig/load.go#L73
Reproduction
Attachment: poc.zip (integration harness) with canonical and control runs.
unzip -q -o poc.zip -d poc
cd poc/poc-F-CADDY-ADMIN-LOAD-001
make test
Expected output (excerpt):
[CALLSITE_HIT]: adminLoad.handleLoad
[PROOF_MARKER]: http_code=200 admin_moved=true response_pwned=true
Control output (excerpt):
[NC_MARKER]: http_code=403 load_blocked=true admin_moved=false response_pwned=false
Suggested remediation
Ensure cross-origin web content cannot trigger POST /load on the local admin API by default, for example by:
- Enabling origin enforcement by default for unsafe methods, and/or
- Requiring an unguessable token for
/load(and other state-changing admin endpoints).
Impact
An attacker can replace the running caddy configuration via the local admin API. Depending on the deployed configuration/modules, this can:
- Change admin listener settings (e.g., move the admin listener to a new address)
- Change HTTP server behavior (e.g., alter routes/responses)
A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones. Typical impact: state-changing actions performed as the victim without their consent.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-27589? CVE-2026-27589 is a medium-severity cross-site request forgery (CSRF) vulnerability in github.com/caddyserver/caddy/v2 (go), affecting versions < 2.11.1. It is fixed in 2.11.1. A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones.
- Which versions of github.com/caddyserver/caddy/v2 are affected by CVE-2026-27589? github.com/caddyserver/caddy/v2 (go) versions < 2.11.1 is affected.
- Is there a fix for CVE-2026-27589? Yes. CVE-2026-27589 is fixed in 2.11.1. Upgrade to this version or later.
- Is CVE-2026-27589 exploitable, and should I be worried? Whether CVE-2026-27589 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-27589 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-27589? Upgrade
github.com/caddyserver/caddy/v2to 2.11.1 or later.