Mint's HTTP/1 Content-Length parser, Mint.HTTP1.Parse.content_length_header/1 in lib/mint/http1/parse.ex, parses the header value with Integer.parse/1, which accepts an optional + or - sign prefix. The length >= 0 guard rejects negatives, but inputs such as +0 or +123 are returned as valid lengths. RFC 7230 specifies Content-Length = 1*DIGIT, with no sign character permitted.
A fronting proxy or load balancer that strictly enforces the grammar will reject or reframe a header like Content-Length: +0, while Mint silently treats it as zero. When Mint reuses the socket (keep-alive, pipelining, or any pooled connection shared across requesters), the parser disagreement is a response-smuggling primitive: the proxy delimits the body one way, Mint another, and bytes from one response get attributed to the next. Where the same Mint connection is shared across trust boundaries, an attacker-controlled upstream can leak bytes into a different consumer's response stream.
This issue affects mint: from 0.1.0 before 1.9.0.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| elixir-mint | mint | unaffected |
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| elixir-mint | mint | unaffected |
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Solution
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Workaround
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Tue, 02 Jun 2026 18:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Metrics |
ssvc
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Tue, 02 Jun 2026 15:45:00 +0000
| Type | Values Removed | Values Added |
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| Description | Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in elixir-mint Mint allows attacker-controlled HTTP/1 servers to desynchronise response framing on shared connections. Mint's HTTP/1 Content-Length parser, Mint.HTTP1.Parse.content_length_header/1 in lib/mint/http1/parse.ex, parses the header value with Integer.parse/1, which accepts an optional + or - sign prefix. The length >= 0 guard rejects negatives, but inputs such as +0 or +123 are returned as valid lengths. RFC 7230 specifies Content-Length = 1*DIGIT, with no sign character permitted. A fronting proxy or load balancer that strictly enforces the grammar will reject or reframe a header like Content-Length: +0, while Mint silently treats it as zero. When Mint reuses the socket (keep-alive, pipelining, or any pooled connection shared across requesters), the parser disagreement is a response-smuggling primitive: the proxy delimits the body one way, Mint another, and bytes from one response get attributed to the next. Where the same Mint connection is shared across trust boundaries, an attacker-controlled upstream can leak bytes into a different consumer's response stream. This issue affects mint: from 0.1.0 before 1.9.0. | |
| Title | HTTP response smuggling in Mint HTTP/1 client via lenient Content-Length parsing | |
| First Time appeared |
Elixir-mint
Elixir-mint mint |
|
| Weaknesses | CWE-444 | |
| CPEs | cpe:2.3:a:elixir-mint:mint:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Elixir-mint
Elixir-mint mint |
|
| References |
| |
| Metrics |
cvssV4_0
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Projects
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MITRE
Status: PUBLISHED
Assigner: EEF
Published:
Updated: 2026-06-02T19:14:42.817Z
Reserved: 2026-06-01T13:45:22.448Z
Link: CVE-2026-49753
Vulnrichment
Updated: 2026-06-02T18:06:34.954Z
NVD
Status : Deferred
Published: 2026-06-02T16:16:44.777
Modified: 2026-06-02T17:18:19.573
Link: CVE-2026-49753
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-06-02T16:45:13Z