Vulnerability 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. Bandit 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. This issue affects bandit: from 1.4.0 before 1.12.5.
Related Weaknesses (CWE)
References
- https://cna.erlef.org/cves/CVE-2026-75484.html
- https://github.com/mtrudel/bandit/commit/d38cf046c9a3cae4d0f88001c2ceb4143f86366
- https://github.com/mtrudel/bandit/security/advisories/GHSA-x3gh-xhj4-3vq8
- https://osv.dev/vulnerability/EEF-CVE-2026-75484
- https://github.com/mtrudel/bandit/security/advisories/GHSA-x3gh-xhj4-3vq8
FAQ
What is CVE-2026-75484?
CVE-2026-75484 is a documented vulnerability. 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 req...
How severe is CVE-2026-75484?
CVSS scoring is not yet available for CVE-2026-75484. Check NVD for updates.
Is there a patch for CVE-2026-75484?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.