{"answers":{"affected":"3 open source packages ship an affected version, including github.com/caddyserver/caddy/v2. It affects 1 product.","exploited":"It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27588 exists.","fix":"Upgrade github.com/caddyserver/caddy/v2 to 2.11.1 or later.","what":"CVE-2026-27588 is a high-severity authentication bypass vulnerability in caddyserver caddy, published on 24 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-27588 and fix it if it is affected.\n\nWhat it is: CVE-2026-27588 is a high-severity authentication bypass vulnerability in caddyserver caddy, published on 24 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27588 exists.\n\nAffected packages and fixed versions:\n- github.com/caddyserver/caddy/v2 (Go): affected all versions; fixed in 2.11.1\n- github.com/caddyserver/caddy/v2 (Go): affected all versions; fixed in 2.11.1\n- github.com/caddyserver/caddy/v2 (Go): affected all versions; fixed in 2.11.1\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-27588/ (Markdown: https://insights.sbomify.com/CVE-2026-27588/index.md)","id":"CVE-2026-27588","markdown":"https://insights.sbomify.com/CVE-2026-27588/index.md","name":"CVE-2026-27588","record":{"aliases":["DEBIAN-CVE-2026-27588","GHSA-x76f-jf84-rqj8","GO-2026-4541","MINI-h35g-r2q2-vh37","UBUNTU-CVE-2026-27588"],"analysis":{"component_type":"server_software","fix_type":"upgrade","impacts":["security_bypass"],"network_reachable":"yes","non_default_config":true,"product_category":"Caddy web server","requires_auth":"none","summary":"Attackers can bypass host-based routing and access controls by manipulating Host header casing when large host lists are configured.","user_interaction":"not_required","vuln_class":"auth_bypass"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"GitHub_M","cpe":[{"product":"caddy","vendor":"caddyserver"}],"cvss":{"score":7.7,"severity":"high","source":"cna","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P","version":"4.0"},"cwes":[{"id":"CWE-178","name":"Improper Handling of Case Sensitivity"}],"description":"Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy's HTTP `host` request matcher is documented as case-insensitive, but when configured with a large host list (\u003e100 entries) it becomes case-sensitive due to an optimized matching path. An attacker can bypass host-based routing and any access controls attached to that route by changing the casing of the `Host` header. Version 2.11.1 contains a fix for the issue.","ecosystems":["Go"],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"weaponised"},"has_fix":true,"headline":"Caddy: MatchHost becomes case-sensitive for large host lists (\u003e100), enabling host-based route/auth bypass","id":"CVE-2026-27588","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"Go","product":null,"products":[],"type":"auth_bypass","year":"2026"},"n_packages":3,"n_references":2,"next":{"headline":"Caddy vulnerable to cross-origin config application via local admin API /load (caddy)","id":"CVE-2026-27589"},"packages":[{"ecosystem":"Go","fixed":["2.11.1"],"introduced":["0"],"last_affected":[],"package":"github.com/caddyserver/caddy/v2","purl":null,"source":"GHSA-x76f-jf84-rqj8"},{"ecosystem":"Go","fixed":["2.11.1"],"introduced":["0"],"last_affected":[],"package":"github.com/caddyserver/caddy/v2","purl":"pkg:golang/github.com/caddyserver/caddy/v2","source":"GHSA-x76f-jf84-rqj8"},{"ecosystem":"Go","fixed":["2.11.1"],"introduced":["0"],"last_affected":[],"package":"github.com/caddyserver/caddy/v2","purl":"pkg:golang/github.com/caddyserver/caddy/v2","source":"GO-2026-4541"}],"prev":{"headline":"Caddy: MatchPath %xx (escaped-path) branch skips case normalization, enabling path-based route/auth bypass","id":"CVE-2026-27587"},"products":["caddy"],"published":"2026-02-24","related":[{"cvss_score":9.8,"headline":"Caddy vulnerable to Authentication Bypass due to mishandling of TLS client authentication","id":"CVE-2018-21246","kev_date_added":null,"published":"2020-06-15"},{"cvss_score":8.9,"headline":"Caddy: Unicode case-folding length expansion causes incorrect split_path index in FastCGI transport","id":"CVE-2026-27590","kev_date_added":null,"published":"2026-02-24"},{"cvss_score":8.8,"headline":"Caddy's mTLS client authentication silently fails open when CA certificate file is missing or malformed","id":"CVE-2026-27586","kev_date_added":null,"published":"2026-02-24"},{"cvss_score":8.1,"headline":"Caddy: Unsafe Unicode Handling in FastCGI splitPos Allows Execution of Non-PHP Files","id":"CVE-2026-45135","kev_date_added":null,"published":"2026-06-23"},{"cvss_score":8.1,"headline":"Caddy: FastCGI header normalization bypass in `forward_auth copy_headers`","id":"CVE-2026-52845","kev_date_added":null,"published":"2026-06-23"},{"cvss_score":8.1,"headline":"Caddy forward_auth copy_headers Does Not Strip Client-Supplied Headers, Allowing Identity Injection and Privilege Escalation","id":"CVE-2026-30851","kev_date_added":null,"published":"2026-03-07"},{"cvss_score":7.7,"headline":"Caddy: MatchPath %xx (escaped-path) branch skips case normalization, enabling path-based route/auth bypass","id":"CVE-2026-27587","kev_date_added":null,"published":"2026-02-24"}],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"CC BY 4.0","name":"GitHub Advisory Database","prefix":"GHSA"},{"class":"attribution","licence":"CC BY 4.0","name":"Go Vulnerability Database","prefix":"GO"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"yes","exploitation":"poc","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-02-27","vendors":["caddyserver"]},"summary":"Attackers can bypass host-based routing and access controls by manipulating Host header casing when large host lists are configured.","url":"https://insights.sbomify.com/CVE-2026-27588/"}