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TI-2026-21977 Aliases CVE-2026-27589GHSA-879p-475x-rqh2

Caddy vulnerable to cross-origin config application via local admin API /load (caddy)

Priority MEDIUM 64CWE-352Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
Present
Impact type
Tampering
Confidentiality · integrity · availability
None · High · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-352.

Summary

Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, 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. Version 2.11.1 contains a fix for the issue.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00195 9th percentileScored 2026-11-07
Public exploit Yes 3 exploit referencesTagged by NVD
Fix Fixed caddy (caddyserver): 2.11.1github.com/caddyserver/caddy/v2 (Go): 2.11.1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

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

Affected products

VendorProductAffected versionsFixed inStatusSource
caddyservercaddybefore 2.11.12.11.1Patch availableCNA
—github.com/caddyserver/caddy/v2 (Go)before 2.11.12.11.1Patch availableGHSA-879p-475x-rqh2
  • caddy Vendorcaddyserver Affected before 2.11.1 Fixed in 2.11.1 Patch available CNA
  • github.com/caddyserver/caddy/v2 (Go) Vendor— Affected before 2.11.1 Fixed in 2.11.1 Patch available GHSA-879p-475x-rqh2

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:caddyserver:caddy:*:*:*:*:*:*:*:*before 2.11.1Vulnerablecaddyserver
  • cpe:2.3:a:caddyserver:caddy:*:*:*:*:*:*:*:* Versions before 2.11.1 Vulnerable ·caddyserver

Remediation

  • Fix · CNA caddy (caddyserver) Fixed in 2.11.1
  • Fix · GHSA-879p-475x-rqh2 github.com/caddyserver/caddy/v2 (Go) Fixed in 2.11.1 Advisory →

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-27589
  2. 2026-10-03 Alias added: GHSA-879p-475x-rqh2

References

Exploit 3

Advisory 1

Other 4

  • TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
  • TI-2026-21978 Improper input validation in caddyserver caddy CVSS 4.0HIGH 8.9
  • TI-2026-21974 Caddy's mTLS client authentication silently fails open when CA certificate file is missing or malformed CVSS 4.0HIGH 8.8
  • TI-2026-23680 Improper authentication in caddyserver caddy CVSS 3.1HIGH 8.8
  • TI-2026-21976 Caddy: MatchHost becomes case-sensitive for large host lists (>100), enabling host-based route/auth bypass CVSS 4.0HIGH 7.7
  • TI-2026-21975 Caddy: MatchPath %xx (escaped-path) branch skips case normalization, enabling path-based route/auth bypass CVSS 4.0HIGH 7.7
See all 19 →

Sources

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