Response smuggling via signed Content-Length acceptance
Published Jun 2, 2026 · Updated Jun 2, 2026
HTTP response smuggling in Elixir Mint before 1.9.0 allows remote attackers controlling an HTTP/1 server to desynchronize shared connections. Mint.HTTP1.Parse.content_length_header/1 passes the trimmed header to Integer.parse/1, which accepts a leading plus sign as part of a valid nonnegative length. Exploitation requires a strict intermediary and reuse of one Mint connection across trust boundaries, allowing attacker-supplied bytes to enter another consumer's response stream.
Summary
What happened
HTTP response smuggling in Elixir Mint before 1.9.0 allows remote attackers controlling an HTTP/1 server to desynchronize shared connections. Mint.HTTP1.Parse.content_length_header/1 passes the trimmed header to Integer.parse/1, which accepts a leading plus sign as part of a valid nonnegative length. Exploitation requires a strict intermediary and reuse of one Mint connection across trust boundaries, allowing attacker-supplied bytes to enter another consumer's response stream.
The record
- CVE
- CVE-2026-49753
- Published
- Jun 2, 2026
- Updated
- Jun 2, 2026
- Vendor
- Elixir Mint
- Product
- Mint
- Classifications
- CWE-444, CAPEC-273
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 2, 2026CVE publishedPublication date reported by the CVE source.
- Jun 2, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0.1.0 <1.9.0
- Affected versionversion=65e0e86d799a6d3b08e4372fccdd9747535e0dd6 <47e48027480228e4e32a0b4df39db497b4804921
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- GHSA-mjqx-c6f6-7rc2 raw TCP response-smuggling proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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