{"answers":{"affected":"5 open source packages ship an affected version, including cowlib, cowboy and gun. It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-43966 in the wild and no public exploit code.","fix":"Apply the vendor's patch.","what":"CVE-2026-43966 is a medium-severity vulnerability in ninenines cowlib, published on 8 Jun 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-2026-43966 and fix it if it is affected.\n\nWhat it is: CVE-2026-43966 is a medium-severity vulnerability in ninenines cowlib, published on 8 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-43966 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- cowlib (Hex): affected from 2.9.0; no fix listed\n- cowboy (Hex): affected all versions; fixed in 2.16.0\n- cowboy (Hex): affected all versions; fixed in 2.16.0\n- gun (Hex): affected all versions; fixed in 2.16.0\n- gun (Hex): affected all versions; fixed in 2.16.0\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-2026-43966/ (Markdown: https://insights.sbomify.com/CVE-2026-43966/index.md)","id":"CVE-2026-43966","markdown":"https://insights.sbomify.com/CVE-2026-43966/index.md","name":"CVE-2026-43966","record":{"aliases":["AZL-90162","DEBIAN-CVE-2026-43966","EEF-CVE-2026-43966","GHSA-w4f7-4cxr-rv3c"],"analysis":{"component_type":"library","fix_type":"patch","impacts":["data_modify","security_bypass"],"network_reachable":"yes","non_default_config":false,"product_category":"Erlang HTTP library","requires_auth":"none","summary":"Attackers can inject CRLF sequences into HTTP headers via cowlib, enabling HTTP response splitting and potential cache poisoning or XSS.","user_interaction":"not_required","vuln_class":"other"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"EEF","cpe":[{"product":"cowlib","vendor":"ninenines"}],"cvss":{"score":6.3,"severity":"medium","source":"cna","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N","version":"4.0"},"cwes":[{"id":"CWE-113","name":"Improper Neutralization of CRLF Sequences in HTTP Headers"}],"description":"Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in ninenines cowlib allows HTTP response splitting via non-VCHAR bytes in structured-fields string values.\n\ncow_http_struct_hd:escape_string/2 in cowlib only escapes \\ and \", passing all other bytes through verbatim. This creates an encoder/decoder asymmetry: the matching parser accepts only printable ASCII (0x20–0x7E, excluding \" and \\), but the encoder emits any byte including CR and LF. An application that builds a structured HTTP header via cow_http_struct_hd:item/1 (or a higher-level wrapper such as cow_http_hd:wt_protocol/1) from attacker-controlled input can have \\r\\n injected into the serialized header value. Once on the wire, the injected CRLF terminates the current header and any following bytes are interpreted as a new header, enabling HTTP response splitting.\n\nThis issue affects cowlib: from 2.9.0 onward.","ecosystems":["Hex"],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"HTTP Response Splitting via Non-VCHAR Bytes in cow_http_struct_hd:escape_string/2","id":"CVE-2026-43966","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"Hex","product":null,"products":[],"type":"other","year":"2026"},"n_packages":5,"n_references":6,"next":{"headline":"Quadratic fragment-name uniqueness check causes denial of service in absinthe","id":"CVE-2026-43967"},"packages":[{"ecosystem":"Hex","fixed":["2.16.0"],"introduced":["0"],"last_affected":[],"package":"cowboy","purl":null,"source":"GHSA-w4f7-4cxr-rv3c"},{"ecosystem":"Hex","fixed":["2.16.0"],"introduced":["0"],"last_affected":[],"package":"cowboy","purl":"pkg:hex/cowboy","source":"GHSA-w4f7-4cxr-rv3c"},{"ecosystem":"Hex","fixed":[],"introduced":["2.9.0"],"last_affected":[],"package":"cowlib","purl":"pkg:hex/cowlib","source":"EEF-CVE-2026-43966"},{"ecosystem":"Hex","fixed":["2.16.0"],"introduced":["0"],"last_affected":[],"package":"gun","purl":null,"source":"GHSA-w4f7-4cxr-rv3c"},{"ecosystem":"Hex","fixed":["2.16.0"],"introduced":["0"],"last_affected":[],"package":"gun","purl":"pkg:hex/gun","source":"GHSA-w4f7-4cxr-rv3c"}],"prev":{"headline":"Path Traversal in build/packages/packages.toml Allows Arbitrary Directory Deletion","id":"CVE-2026-43965"},"products":["cowlib"],"published":"2026-06-08","related":[{"cvss_score":8.7,"headline":"Unbounded chunk-size hex digits in cowlib cause quadratic CPU and memory DoS","id":"CVE-2026-7790","kev_date_added":null,"published":"2026-05-11"},{"cvss_score":6.3,"headline":"CR Injection in SSE Encoder Enables Event Splitting via cow_sse:event/1","id":"CVE-2026-43968","kev_date_added":null,"published":"2026-05-11"},{"cvss_score":2.1,"headline":"Cookie Request Header Injection via Unvalidated Encoder in cow_cookie:cookie/1","id":"CVE-2026-43969","kev_date_added":null,"published":"2026-05-11"}],"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":"CC BY 4.0","name":"GitHub Advisory Database","prefix":"GHSA"},{"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":"no","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-10-14","vendors":["ninenines"]},"summary":"Attackers can inject CRLF sequences into HTTP headers via cowlib, enabling HTTP response splitting and potential cache poisoning or XSS.","url":"https://insights.sbomify.com/CVE-2026-43966/"}