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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-59246?
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
Which versions are affected by CVE-2026-59246?
1 open source package ship an affected version, including mint.
| Package | 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.
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-2026-59246 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59246 exists.
Sources
Also known as EEF-CVE-2026-59246, GHSA-8pf6-g464-h6h9.