Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')

### Summary Insufficient validation of outbound header values may lead to request splitting or response splitting attacks in scenarios where attackers have sufficient control over outbound headers. ### Details Outbound `trillium_http::HeaderValue` and `trillium_http::HeaderName` can be constructed infallibly and were not checked for illegal bytes when sending requests. Thus, if an attacker has sufficient control over header values (or names) in a request that they could inject `\r\n` sequences, they could get the client and server out of sync, and then pivot to gain control over other parts of requests or responses. (i.e. exfiltrating data from other requests, SSRF, etc.) ### Patches #### trillium-client >= 0.5.4: * If any header name or header value is invalid in the client request headers, awaiting the client Conn returns an `Error::MalformedHeader` prior to any network access. ### Workarounds trillium client applications should sanitize or validate untrusted input that is included in header values and header names. Carriage return, newline, and null characters are not allowed. ### Impact This only affects use cases where attackers have control of outbound headers, and can insert "\r\n" sequences. Specifically, if untrusted and unvalidated input is inserted into header names or values. ### Credit Discovered and reported by [@divergentdave](https://github.com/divergentdave)

Source published

23 Jan 2024 12:00:00 UTC

Source modified

12 Oct 2026 18:00:04 UTC

Observed here

24 Oct 2026 13:19:54 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.