CVE-2026-49754: HTTP/2 CONTINUATION flood in Mint client via unbounded header-block accumulation

Severity: high (CVSS 8.2 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-02 · updated 2026-07-22
Weakness: CWE-770

Description

Allocation of Resources Without Limits or Throttling vulnerability in elixir-mint Mint allows attacker-controlled HTTP/2 servers to exhaust memory in a Mint client (HTTP/2 CONTINUATION flood). When Mint's HTTP/2 receive path observes a HEADERS frame without the END_HEADERS flag, the unparsed header-block fragment is parked in conn.headers_being_processed, and every subsequent CONTINUATION frame on that stream is appended to the accumulator. Nothing in the receive path caps the accumulator: there is no per-stream size limit, no CONTINUATION frame-count limit, and max_header_list_size is only enforced on outgoing requests, never on inbound header blocks (its default is :infinity). A malicious or compromised HTTP/2 server can stream an endless sequence of CONTINUATION frames (each up to the peer-advertised SETTINGS_MAX_FRAME_SIZE) and drive the client's iolist to arbitrary size, causing memory exhaustion and BEAM process death. A single connection to an attacker-controlled HTTP/2 endpoint is sufficient. This issue affects mint: from 0.1.0 before 1.9.0.

Affected products

elixir-mint mint: from 0.1.0 before 1.9.0 — fixed in 1.9.0

How to fix

Upgrade to a fixed version: elixir-mint mint 1.9.0. Check the vendor advisory for mitigations.

References

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