{"id":"CVE-2026-75484","state":"PUBLISHED","title":"HTTP/2 header field values containing CR, LF or NUL are passed to the application unvalidated in Bandit","description":"Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in mtrudel bandit allows an unauthenticated remote attacker to smuggle CR, LF, or NUL characters into application-visible request headers via HTTP/2. Bandit.HTTP2.Stream.read_headers/1 validates pseudo-header placement and uniqueness, header-name casing, connection-specific headers, the te value, and content-length, but never checks field values. Because HPACK carries arbitrary octets, a HEADERS block whose field values contain \\r, \\n, or \\0 decodes without error and the values land in conn.req_headers unchanged. The HTTP/1 path already rejects the same octets; HTTP/2 did not.\n\nBandit itself is not a sink for the injected bytes: its own logging uses fixed strings or inspect, and HTTP/2 response headers are HPACK-encoded and separately rejected by Plug's put_resp_header, so response splitting is not reachable through this path. The risk is entirely in how a downstream application consumes header values, such as appending one verbatim to a plain-text log or concatenating it into an upstream request. A related gap bundled in the same fix: only :method, :scheme, and :path were checked for at most one occurrence; a duplicate :authority pseudo-header was accepted, with the first instance silently winning as conn.host while a conflicting value remained visible to the application.\n\nThis issue affects bandit: from 1.4.0 before 1.12.5.","publishedAt":"2026-08-20T21:11:27.523Z","updatedAt":"2026-08-21T19:52:42.954Z","severity":{"score":6.9,"label":"Medium","version":"4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","source":"EEF"},"assigner":"EEF","products":["mtrudel bandit"],"affected":[{"vendor":"mtrudel","product":"bandit","packageName":"bandit","packageURL":"pkg:hex/bandit","defaultStatus":"unaffected","versions":[{"version":"1.4.0","status":"affected","lessThan":"1.12.5","versionType":"semver"}],"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"],"modules":["'Elixir.Bandit.HTTP2.Stream'"],"programFiles":["lib/bandit/http2/stream.ex"],"programRoutines":[{"name":"'Elixir.Bandit.HTTP2.Stream':read_headers/1"}],"repo":"https://github.com/mtrudel/bandit"},{"vendor":"mtrudel","product":"bandit","packageName":"mtrudel/bandit","packageURL":"pkg:github/mtrudel/bandit","defaultStatus":"unaffected","versions":[{"version":"fff06efe3be962b484bd4d3eb339372fda5a231f","status":"affected","lessThan":"d38cf046c9a3cae4d0f88001c2ceb4143f86366b","versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"],"modules":["'Elixir.Bandit.HTTP2.Stream'"],"programFiles":["lib/bandit/http2/stream.ex"],"programRoutines":[{"name":"'Elixir.Bandit.HTTP2.Stream':read_headers/1"}],"repo":"https://github.com/mtrudel/bandit"}],"references":["https://github.com/mtrudel/bandit/security/advisories/GHSA-x3gh-xhj4-3vq8","https://cna.erlef.org/cves/CVE-2026-75484.html","https://osv.dev/vulnerability/EEF-CVE-2026-75484","https://github.com/mtrudel/bandit/commit/d38cf046c9a3cae4d0f88001c2ceb4143f86366b"],"weaknesses":["CWE-93"],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/75xxx/CVE-2026-75484.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-75484","state":"PUBLISHED","datePublished":"2026-08-20T21:11:27.523Z","dateUpdated":"2026-08-21T19:52:42.954Z","assignerShortName":"EEF","assignerOrgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","dateReserved":"2026-08-18T10:30:01.764Z"},"containers":{"cna":{"title":"HTTP/2 header field values containing CR, LF or NUL are passed to the application unvalidated in Bandit","descriptions":[{"lang":"en","value":"Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in mtrudel bandit allows an unauthenticated remote attacker to smuggle CR, LF, or NUL characters into application-visible request headers via HTTP/2. Bandit.HTTP2.Stream.read_headers/1 validates pseudo-header placement and uniqueness, header-name casing, connection-specific headers, the te value, and content-length, but never checks field values. Because HPACK carries arbitrary octets, a HEADERS block whose field values contain \\r, \\n, or \\0 decodes without error and the values land in conn.req_headers unchanged. The HTTP/1 path already rejects the same octets; HTTP/2 did not.\n\nBandit itself is not a sink for the injected bytes: its own logging uses fixed strings or inspect, and HTTP/2 response headers are HPACK-encoded and separately rejected by Plug's put_resp_header, so response splitting is not reachable through this path. The risk is entirely in how a downstream application consumes header values, such as appending one verbatim to a plain-text log or concatenating it into an upstream request. A related gap bundled in the same fix: only :method, :scheme, and :path were checked for at most one occurrence; a duplicate :authority pseudo-header was accepted, with the first instance silently winning as conn.host while a conflicting value remained visible to the application.\n\nThis issue affects bandit: from 1.4.0 before 1.12.5."}],"affected":[{"vendor":"mtrudel","product":"bandit","packageName":"bandit","packageURL":"pkg:hex/bandit","defaultStatus":"unaffected","versions":[{"version":"1.4.0","status":"affected","lessThan":"1.12.5","versionType":"semver"}],"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"],"modules":["'Elixir.Bandit.HTTP2.Stream'"],"programFiles":["lib/bandit/http2/stream.ex"],"programRoutines":[{"name":"'Elixir.Bandit.HTTP2.Stream':read_headers/1"}],"repo":"https://github.com/mtrudel/bandit"},{"vendor":"mtrudel","product":"bandit","packageName":"mtrudel/bandit","packageURL":"pkg:github/mtrudel/bandit","defaultStatus":"unaffected","versions":[{"version":"fff06efe3be962b484bd4d3eb339372fda5a231f","status":"affected","lessThan":"d38cf046c9a3cae4d0f88001c2ceb4143f86366b","versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"],"modules":["'Elixir.Bandit.HTTP2.Stream'"],"programFiles":["lib/bandit/http2/stream.ex"],"programRoutines":[{"name":"'Elixir.Bandit.HTTP2.Stream':read_headers/1"}],"repo":"https://github.com/mtrudel/bandit"}],"references":[{"url":"https://github.com/mtrudel/bandit/security/advisories/GHSA-x3gh-xhj4-3vq8","tags":["vendor-advisory","related"]},{"url":"https://cna.erlef.org/cves/CVE-2026-75484.html","tags":["related"]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-75484","tags":["related"]},{"url":"https://github.com/mtrudel/bandit/commit/d38cf046c9a3cae4d0f88001c2ceb4143f86366b","tags":["patch"]}],"metrics":[{"cvssV4_0":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"NETWORK","baseScore":6.9,"baseSeverity":"MEDIUM","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"NOT_DEFINED","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"LOW","vulnerabilityResponseEffort":"NOT_DEFINED"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-93","description":"CWE-93 Improper Neutralization of CRLF Sequences ('CRLF Injection')","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"EEF","orgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","dateUpdated":"2026-08-20T21:11:27.523Z"},"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*","versionEndExcluding":"1.12.5","versionStartIncluding":"1.4.0","vulnerable":true}],"negate":false,"operator":"OR"}],"operator":"AND"}],"credits":[{"lang":"en","type":"remediation developer","value":"Mat Trudel"},{"lang":"en","type":"coordinator","value":"Jonatan Männchen / EEF"}],"impacts":[{"capecId":"CAPEC-81","descriptions":[{"lang":"en","value":"CAPEC-81 Web Server Logs Tampering"}]}],"source":{"discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/mtrudel/bandit/security/advisories/GHSA-x3gh-xhj4-3vq8","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-21T19:52:23.602062Z","id":"CVE-2026-75484","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-21T19:52:42.954Z"}}]}}}