{"answers":{"affected":"1 open source package ship an affected version, including cowlib.","exploited":"There is no known exploitation of CVE-2026-43971 in the wild and no public exploit code.","fix":"Upgrade cowlib to 2.20.0 or later.","what":"CVE-2026-43971 is a medium-severity vulnerability in ninenines cowlib, published on 18 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-2026-43971 and fix it if it is affected.\n\nWhat it is: CVE-2026-43971 is a medium-severity vulnerability in ninenines cowlib, published on 18 Aug 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-2026-43971 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- cowlib (Hex): affected from 2.9.0; fixed in 2.20.0\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-2026-43971/ (Markdown: https://insights.sbomify.com/CVE-2026-43971/index.md)","id":"CVE-2026-43971","markdown":"https://insights.sbomify.com/CVE-2026-43971/index.md","name":"CVE-2026-43971","record":{"aliases":["AZL-96873","DEBIAN-CVE-2026-43971","EEF-CVE-2026-43971","GHSA-gg23-fwhr-prjh","RHSA-2026:66210","UBUNTU-CVE-2026-43971"],"analysis":{"component_type":"library","fix_type":"upgrade","impacts":["security_bypass","other"],"network_reachable":"yes","non_default_config":false,"product_category":"Erlang HTTP library","requires_auth":"none","summary":"Attackers can smuggle Link header directives to force victim browsers to connect to attacker-controlled origins via unescaped characters in cowlib.","user_interaction":"not_required","vuln_class":"other"},"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:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N","version":"4.0"},"cwes":[{"id":"CWE-116","name":"Improper Encoding or Escaping of Output"}],"description":"Improper Encoding or Escaping of Output vulnerability in ninenines cowlib allows Link header directive smuggling via unescaped special characters in cow_link:link/1.\n\ncow_link:do_link/1 in cowlib interpolates the target URI, rel value, and attribute keys directly into the serialized Link: header value without escaping or token-grammar validation. A \u003e byte in target prematurely closes the URI slot, allowing an attacker to append additional link entries with attacker-chosen rel directives. A \" or \\ in rel escapes the quoted string and opens new parameters. Any byte — including whitespace, =, and \" — in an attribute key is emitted verbatim. Because browsers act on Link: directives such as rel=\"preconnect\", rel=\"preload\", and rel=\"prerender\", an attacker who can influence these fields in an application that round-trips parsed Link headers through cow_link:link/1 can force victim browsers to make out-of-band connections to attacker-controlled origins.\n\nThis issue affects cowlib: from 2.9.0 before 2.20.0.","ecosystems":["Hex","Red Hat:hummingbird:1"],"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":"Link Header Directive Smuggling via Unescaped target/rel/Attribute Keys in cow_link:link/1","id":"CVE-2026-43971","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"Hex","product":null,"products":[],"type":"other","year":"2026"},"n_packages":2,"n_references":4,"next":{"headline":"gun HTTP/2 PUSH_PROMISE authority not validated against connection origin allows cross-origin cookie injection","id":"CVE-2026-43972"},"packages":[{"ecosystem":"Hex","fixed":["2.20.0"],"introduced":["2.9.0"],"last_affected":[],"package":"cowlib","purl":"pkg:hex/cowlib","source":"EEF-CVE-2026-43971"},{"ecosystem":"Red Hat:hummingbird:1","fixed":["0:4.3.5-1.1.hum1"],"introduced":["0"],"last_affected":[],"package":"rabbitmq-server4.3","purl":"pkg:rpm/redhat/rabbitmq-server4.3","source":"RHSA-2026:66210"}],"prev":{"headline":"Decompression Bomb in cow_spdy:inflate/2 Allows Memory Exhaustion via Crafted SPDY Frame","id":"CVE-2026-43970"},"products":["cowlib"],"published":"2026-08-18","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":"CC BY 4.0","name":"Red Hat","prefix":"RHSA"},{"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":"2026-09-16","vendors":["ninenines"]},"summary":"Attackers can smuggle Link header directives to force victim browsers to connect to attacker-controlled origins via unescaped characters in cowlib.","url":"https://insights.sbomify.com/CVE-2026-43971/"}