{"answers":{"affected":"1 open source package ship an affected version, including oidcc_plug.","exploited":"It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-66883 exists.","fix":"Upgrade oidcc_plug to 0.5.0 or later.","what":"CVE-2026-66883 is a medium-severity vulnerability in Erlang Ecosystem Foundation oidcc_plug, published on 4 Aug 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-2026-66883 and fix it if it is affected.\n\nWhat it is: CVE-2026-66883 is a medium-severity vulnerability in Erlang Ecosystem Foundation oidcc_plug, published on 4 Aug 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-2026-66883 exists.\n\nAffected packages and fixed versions:\n- oidcc_plug (Hex): affected from 0.1.0-alpha.3; fixed in 0.5.0\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-2026-66883/ (Markdown: https://insights.sbomify.com/CVE-2026-66883/index.md)","id":"CVE-2026-66883","markdown":"https://insights.sbomify.com/CVE-2026-66883/index.md","name":"CVE-2026-66883","record":{"aliases":["EEF-CVE-2026-66883","GHSA-w5r8-m75h-98fc"],"analysis":{"component_type":"library","fix_type":"patch","impacts":["security_bypass"],"network_reachable":"yes","non_default_config":true,"product_category":"Erlang OIDC library","requires_auth":"none","summary":"Case-sensitive header lookup disables user agent session binding, allowing stolen session replay from different clients if the feature is enabled.","user_interaction":"not_required","vuln_class":"security_feature_bypass"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"EEF","cpe":[],"cvss":{"score":6.3,"severity":"medium","source":"cna","vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","version":"4.0"},"cwes":[{"id":"CWE-178","name":"Improper Handling of Case Sensitivity"}],"description":"Improper Handling of Case Sensitivity vulnerability in Erlang Ecosystem Foundation oidcc_plug (Oidcc.Plug.Authorize module) renders the user agent session binding inert, removing a defense in depth control against replay of a stolen session.\n\nThis vulnerability is associated with program files lib/oidcc/plug/authorize.ex and lib/oidcc/plug/authorization_callback.ex, and program routines Oidcc.Plug.Authorize.call/2 and Oidcc.Plug.AuthorizationCallback.call/2.\n\nOidcc.Plug.Authorize.call/2 reads the initiating client's user agent with get_req_header(conn, \"User-Agent\"). Plug lowercases incoming header names, but get_req_header/2 matches the supplied key exactly and performs no normalization of its own, so the mixed-case lookup always returns an empty list and nil is written into the session. On the callback side, Oidcc.Plug.AuthorizationCallback treats a stored nil user agent as nothing to compare and returns :ok without inspecting the request. The two behaviours combine so that the check passes unconditionally on every request, including for deployments that explicitly opted in with check_useragent: true, and an authorization callback can be completed from a different user agent than the one that initiated the flow without detection. The check fails open silently, with no error and no log entry, so a deployment cannot tell the binding is absent.\n\nThe impact is limited to defense in depth. The inert check does not by itself allow an attacker to complete an authorization flow; it removes one layer that would otherwise hinder use of a stolen or leaked session, such as an exfiltrated session cookie replayed from a different client. The CSRF/state, nonce, and PKCE checks are unaffected and continue to function. Deployments that never enabled check_useragent are not affected in practice, since they never expected the binding. The corresponding lookup in Oidcc.Plug.AuthorizationCallback correctly uses the lowercase key and is not affected.\n\nThis issue affects oidcc_plug: from 0.1.0-alpha.3 before 0.5.0.","ecosystems":["Hex"],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"weaponised"},"has_fix":true,"headline":"Oidcc.Plug.Authorize user agent session binding inert due to case-sensitive header lookup","id":"CVE-2026-66883","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"Hex","product":null,"products":[],"type":"security_feature_bypass","year":"2026"},"n_packages":1,"n_references":4,"next":{"headline":"Cross-site request forgery in oidcc plug","id":"CVE-2026-66884"},"packages":[{"ecosystem":"Hex","fixed":["0.5.0"],"introduced":["0.1.0-alpha.3"],"last_affected":[],"package":"oidcc_plug","purl":"pkg:hex/oidcc_plug","source":"EEF-CVE-2026-66883"}],"prev":{"headline":"Reflected XSS in AshAuthentication confirmation and magic link interaction forms","id":"CVE-2026-66882"},"products":["oidcc_plug"],"published":"2026-08-04","related":[],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"CC BY 4.0","name":"Erlang Ecosystem Foundation","prefix":"EEF"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"no","exploitation":"poc","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-08-04","vendors":["Erlang Ecosystem Foundation"]},"summary":"Case-sensitive header lookup disables user agent session binding, allowing stolen session replay from different clients if the feature is enabled.","url":"https://insights.sbomify.com/CVE-2026-66883/"}