CVE-2026-48861 — mint
Fix: elixir-mint/mint@fad0914CVE-2026-48861 is a CWE-93 vulnerability in mint. A fix is available for mint — see the affected versions and patch details below.
CRLF injection in HTTP/1 request line via unvalidated method in Mint
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-48861.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
Real-World Exposure
mintReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Hex packages — download data is not available via public APIs for these ecosystems.
Description
Summary
Mint's HTTP/1 request encoder splices the caller-supplied method and target directly into the request line without character validation. An application that forwards attacker-controlled input as the HTTP method or the target to Mint.HTTP.request/5 is exposed to request-line CRLF injection, allowing the attacker to terminate the request line early, inject arbitrary headers, and pipeline a fully attacker-chosen second request onto the same TCP connection.
Details
encode_request_line/2 in lib/mint/http1/request.ex writes method and target to the wire verbatim. encode_headers/1 validates header names and values, but there is no equivalent validate_method!/1.
Mint 1.7.0 added validate_request_target/2, which rejects CRLF and other control characters in target by default and closes the path/query vector. The method field remains unvalidated, so a CRLF-bearing method such as "GET / HTTP/1.1\r\nX-Smuggled: 1\r\nGET /admin" is accepted and written to the socket as-is. Bytes after the first \r\n are interpreted by the peer as an injected header, or, with a second \r\n, as an additional pipelined request.
PoC
- Stand up a Mint-using gateway/proxy that calls
Mint.HTTP.request(conn, method, "/", [], nil)withmethodtaken from caller input. - Send a request whose forwarded method is
"GET / HTTP/1.1\r\nX-Smuggled-Header: pwned\r\nGET /admin/delete-everything". - Observe the bytes received by the upstream server: the smuggled header line and the second request line appear verbatim in the outbound stream.
Impact
CRLF injection / HTTP request smuggling in the HTTP/1 client encoder, exploitable under default configuration whenever an application passes caller-influenced input as the HTTP method. An attacker who controls the method can inject arbitrary outbound headers (forged Host, Authorization, cache-poisoning headers) and smuggle additional, fully attacker-chosen requests to the upstream server over the same connection, potentially reaching endpoints the legitimate caller never intended to invoke.
Resources
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💧Hex | mint | all versions | 1.9.0mix deps.update mint |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mint, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update mint to 1.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-48861 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2026-48861 in your dependencies?
Find it across Hex, including transitive dependencies.