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8.1
CVE-2026-82672: Mint client may misread chunked responses, causing smearing
CVE-2026-82672 · published 1 month ago
Summary
The Mint library used by Elixir applications can treat specially crafted pieces of a server's reply as valid, even though strict network devices would reject them. This mismatch can let a malicious server confuse the client and insert false data into later requests over the same connection. Update Mint to version 1.10.1 or newer to fix the issue.
What to do
- Update mint to version 1.10.1.
- Update ericmj mint to version 1.10.1.
Affected software
| Ecosystem | Vendor | Product | Affected versions |
|---|---|---|---|
| Hex | – | mint |
>= 0.1.0, < 1.10.1 Fix: upgrade to 1.10.1
|
| – | elixir-mint | mint |
< 1.10.1 < c82377838dc6e275ef40bafa664fbcdf50270c60 |
| Hex | ericmj | mint |
>= 0.1.0, < 1.10.1 Fix: upgrade to 1.10.1
|
Original advisory text
Unvalidated chunk-size line tail in Mint HTTP/1 client enables response smuggling against strict intermediaries on pooled connections
Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') vulnerability in elixir-mint mint allows a malicious HTTP/1 server to desynchronize a strict intermediary and the Mint client on a pooled connection, enabling response-queue poisoning against subsequent requests that share the connection.
Mint.HTTP1.Parse.chunk_size/1 in lib/mint/http1/parse.ex stops at the first non-hexadecimal byte of a chunked response's chunk-size line and returns the remainder unexamined. Mint.HTTP1.decode_body/5 in lib/mint/http1.ex then discards every byte up to the CRLF with Parse.ignore_until_crlf/1, so the accepted grammar is a run of hex digits followed by arbitrary bytes, where RFC 9112 permits only a ;-introduced chunk extension. Lines such as 5ZZZZZ and 5 9 are accepted as chunk size 5, and 0ZZZZ is accepted as the terminating chunk that ends the message body. An RFC-strict intermediary rejects such a line while Mint accepts it, so the two disagree on chunk boundaries and on where the response ends.
This issue affects mint: from 0.1.0 before 1.10.1.
Mint.HTTP1.Parse.chunk_size/1 in lib/mint/http1/parse.ex stops at the first non-hexadecimal byte of a chunked response's chunk-size line and returns the remainder unexamined. Mint.HTTP1.decode_body/5 in lib/mint/http1.ex then discards every byte up to the CRLF with Parse.ignore_until_crlf/1, so the accepted grammar is a run of hex digits followed by arbitrary bytes, where RFC 9112 permits only a ;-introduced chunk extension. Lines such as 5ZZZZZ and 5 9 are accepted as chunk size 5, and 0ZZZZ is accepted as the terminating chunk that ends the message body. An RFC-strict intermediary rejects such a line while Mint accepts it, so the two disagree on chunk boundaries and on where the response ends.
This issue affects mint: from 0.1.0 before 1.10.1.
References
- https://cna.erlef.org/cves/CVE-2026-82672.html URL
- https://hex.pm/packages/mint Product
- https://github.com URL
- https://repo.hex.pm URL
- https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82672... Vendor Advisory
- https://nvd.nist.gov/vuln/detail/CVE-2026-82672 Vendor Advisory
- https://github.com/elixir-mint/mint Product
- https://osv.dev/vulnerability/EEF-CVE-2026-82672 URL
- https://github.com/elixir-mint/mint/security/advisories/GHSA-rj5m-69wp-cxq9 Vendor Advisory
- https://github.com/elixir-mint/mint/commit/60089586ec7adc9fddb09f69a2f5919ba9ac7... Patch
- https://github.com/elixir-mint/mint/commit/c82377838dc6e275ef40bafa664fbcdf50270... Patch
Internet-facing
60 days
Internal
At next upgrade
- Not known to be exploited
- Needs hands-on effort to exploit
- Gives an attacker partial control
Severity
8.1
High
Type
CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Timeline
Published19 Sep 2026
Updated4 Nov 2026
First seen19 Sep 2026
Sources
CVE-2026-82672 · NVD
CVE-2026-82672 · MITRE
EEF-CVE-2026-82672 · OSV
GHSA-rj5m-69wp-cxq9 · GHSA
CVE-2026-82672 · OSV
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