# CVE-2026-59246: Zero-length HTTP/2 CONTINUATION frames bypass Mint's header-block byte-size cap and exhaust client memory

> A malicious HTTP/2 server can exhaust client memory by sending infinite zero-length CONTINUATION frames, causing denial of service in the Mint library.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/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:** 14 Jul 2026
- **Updated:** 14 Jul 2026
- **Also known as:** EEF-CVE-2026-59246, GHSA-8pf6-g464-h6h9

## What is CVE-2026-59246?

CVE-2026-59246 is a medium-severity denial of service vulnerability in elixir-mint mint, published on 14 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 vulnerability in elixir-mint mint allows a remote HTTP/2 server to exhaust memory on the client host and cause a denial of service.

The Mint.HTTP2.handle_continuation/3 function in lib/mint/http2.ex accumulates the header-block fragment carried by each HTTP/2 CONTINUATION frame into a growing conn.headers_being_processed nesting, one level deeper per frame, and only releases it when a frame with the END_HEADERS flag arrives. The only guard on this accumulator is Mint.HTTP2.assert_header_block_within_max_size/2, which sums the byte size of the fragments received so far. Because a CONTINUATION frame is permitted by the protocol to carry a zero-length payload, an unbounded chain of zero-length CONTINUATION frames adds no bytes to the running total, never trips the size cap, and never emits END_HEADERS, yet each frame still nests the accumulator one level deeper.

A malicious HTTP/2 server (reachable directly, via an attacker-controlled redirect, via SSRF, or via a man-in-the-middle) can open a stream by sending a HEADERS frame without END_HEADERS and then stream zero-length CONTINUATION frames indefinitely. Client memory grows one cons cell per frame received; sustained bandwidth from the peer drives the BEAM node running the Mint client to memory exhaustion and eventual out-of-memory termination.

This issue affects mint: from 0.1.0 before 1.9.2.

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

## Which versions are affected by CVE-2026-59246?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `mint` | Hex | From 0.1.0 | 1.9.2 |

## How do I fix CVE-2026-59246?

Upgrade mint to 1.9.2 or later.

## Is CVE-2026-59246 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59246 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-59246 and fix it if it is affected.

What it is: CVE-2026-59246 is a medium-severity denial of service vulnerability in elixir-mint mint, published on 14 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-2026-59246 exists.

Affected packages and fixed versions:
- mint (Hex): affected from 0.1.0; fixed in 1.9.2

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-2026-59246/ (Markdown: https://insights.sbomify.com/CVE-2026-59246/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-59246
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-59246
- OSV: https://osv.dev/vulnerability/CVE-2026-59246

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-59246/
Summaries are generated and may contain mistakes; the official description above is the record.