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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
Which versions are affected by CVE-2026-56810?
1 open source package ship an affected version, including mint.
| Package | 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.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-56810 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-56810 exists.
Sources
Also known as EEF-CVE-2026-56810, GHSA-c59h-fq4p-r36r.