# CVE-2026-48861: CRLF injection in HTTP/1 request line via unvalidated method in Mint

> Attackers can inject CRLF sequences into HTTP request lines via unvalidated method fields, enabling request smuggling and header injection in applications using the Mint library.

- **Severity:** Low 2.1 (`CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 2 Jun 2026
- **Updated:** 2 Jun 2026
- **Also known as:** EEF-CVE-2026-48861, GHSA-2pg6-44cx-c49v

## What is CVE-2026-48861?

CVE-2026-48861 is a low-severity vulnerability in elixir-mint mint, published on 2 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in elixir-mint Mint allows HTTP Request Splitting and HTTP Request Smuggling.

In lib/mint/http1/request.ex, the encode_request_line/2 function splices the caller-supplied method and target arguments directly into the HTTP/1 request line without any character validation: [method, ?\s, target, " HTTP/1.1\r\n"]. An application that forwards attacker-controlled input as the HTTP method or target to Mint.HTTP.request/5 is therefore exposed to request-line CRLF injection: the attacker can terminate the request line early, inject arbitrary headers, and smuggle an entirely separate pipelined HTTP request onto the same TCP connection.

Mint 1.7.0 introduced validate_request_target/2, which rejects CRLF and other control characters in the target by default and closes the path/query vector unless the caller opts out via skip_target_validation: true. The method field remains unvalidated, so the method-based injection is exploitable under the default Mint configuration on all versions.

This issue affects mint: from 0.1.0 before 1.9.0.

Weakness: CWE-93 (Improper Neutralization of CRLF Sequences)

## Which versions are affected by CVE-2026-48861?

3 open source packages ship an affected version, including mint.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mint` | Hex | All versions | 1.9.0 |
| `mint` | Hex | All versions | 1.9.0 |
| `mint` | Hex | From 0.1.0 | 1.9.0 |

## How do I fix CVE-2026-48861?

Upgrade mint to 1.9.0 or later.

## Is CVE-2026-48861 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-48861 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-48861 and fix it if it is affected.

What it is: CVE-2026-48861 is a low-severity vulnerability in elixir-mint mint, published on 2 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-48861 exists.

Affected packages and fixed versions:
- mint (Hex): affected all versions; fixed in 1.9.0
- mint (Hex): affected all versions; fixed in 1.9.0
- mint (Hex): affected from 0.1.0; fixed in 1.9.0

Task:
1. 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.
2. 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.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-48861/ (Markdown: https://insights.sbomify.com/CVE-2026-48861/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-48861
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-48861
- OSV: https://osv.dev/vulnerability/CVE-2026-48861

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-48861/
Summaries are generated and may contain mistakes; the official description above is the record.