# CVE-2026-56810: mint buffers an entire chunked response chunk in memory in Mint.HTTP1.decode_body/5

> A malicious server can cause an out-of-memory denial of service in the Mint HTTP client by sending oversized chunked responses.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Jul 2026
- **Updated:** 7 Jul 2026
- **Also known as:** EEF-CVE-2026-56810, GHSA-c59h-fq4p-r36r

## What is CVE-2026-56810?

CVE-2026-56810 is a high-severity denial of service vulnerability in elixir-mint mint, published on 6 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Allocation of Resources Without Limits or Throttling vulnerability in elixir-mint mint (Mint.HTTP1 module) allows a denial of service via an oversized chunked transfer-encoded response.

This vulnerability is associated with program files lib/mint/http1.ex and program routines 'Elixir.Mint.HTTP1':decode_body/5, 'Elixir.Mint.HTTP1':add_body_to_buffer/2.

When Mint decodes a chunked HTTP response body, it accumulates each partial fragment of the current chunk in the connection's data_buffer (an unbounded iolist) via add_body_to_buffer/2 and does not emit the data to the caller until the full declared chunk length has been received. The chunk size is taken directly from the server and parsed with no upper bound, so a malicious or compromised server can announce one enormous chunk (for example a size line of 7FFFFFFF, about 2 GiB) and then send the body bytes slowly without ever completing the chunk. The client buffers every received byte while it waits for a completion that never arrives, and because no data responses are produced until the chunk finishes, a caller that otherwise streams large content-length bodies safely gains no protection. An unauthenticated remote server (reachable whenever a client follows redirects, fetches user-supplied URLs, or processes webhooks) can drive the client's memory arbitrarily high and trigger an out-of-memory condition.

This issue affects mint: from 0.5.0 before 1.9.1.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-56810?

1 open source package ship an affected version, including mint.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mint` | Hex | From 0.5.0 | 1.9.1 |

## How do I fix CVE-2026-56810?

Upgrade mint to 1.9.1 or later.

## Is CVE-2026-56810 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-56810 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-56810 and fix it if it is affected.

What it is: CVE-2026-56810 is a high-severity denial of service vulnerability in elixir-mint mint, published on 6 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-56810 exists.

Affected packages and fixed versions:
- mint (Hex): affected from 0.5.0; fixed in 1.9.1

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-2026-56810/ (Markdown: https://insights.sbomify.com/CVE-2026-56810/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-56810
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-56810
- OSV: https://osv.dev/vulnerability/CVE-2026-56810

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-56810/
Summaries are generated and may contain mistakes; the official description above is the record.