Summary
mint: Unbounded CONTINUATION/HEADERS frame accumulation (CONTINUATION flood)
Mint's HTTP/2 client accumulates CONTINUATION header-block fragments into a per-connection buffer with no cap on size or frame count. A malicious or compromised HTTP/2 server can drive the client's memory to arbitrary size by streaming an endless chain of CONTINUATION frames after a HEADERS frame that omits END_HEADERS, causing memory exhaustion and BEAM process death. A single connection to an attacker-controlled HTTP/2 endpoint is sufficient.
Details
When Mint's HTTP/2 receive path observes a HEADERS frame without the END_HEADERS flag, 'Elixir.Mint.HTTP2':handle_headers/3 parks the unparsed header-block fragment in conn.headers_being_processed. Every subsequent CONTINUATION frame on that stream is then appended to the accumulator by 'Elixir.Mint.HTTP2':handle_continuation/3.
Nothing in the receive path bounds this accumulator: there is no per-stream size cap, no CONTINUATION frame-count cap, and max_header_list_size is only enforced on outgoing requests (its default is :infinity, and the only enforcement helper inspects server_settings for request encoding, never inbound header blocks). Each CONTINUATION payload can be up to the peer-advertised SETTINGS_MAX_FRAME_SIZE, so the attacker can grow headers_being_processed to arbitrary size at line rate.
PoC
- Stand up a raw TCP server that speaks the HTTP/2 handshake.
- After the client's request
HEADERSarrives, respond with aHEADERSframe on stream 1 withflags = 0(noEND_HEADERS, noEND_STREAM) and an empty header-block fragment. - Stream
CONTINUATIONframes on stream 1, each withflags = 0and a payload up toSETTINGS_MAX_FRAME_SIZE. Never setEND_HEADERS. - The client's process memory grows linearly with the flood and the BEAM process eventually crashes with OOM.
Workarounds
Restrict Mint to HTTP/1 on connections to untrusted servers by passing protocols: [:http1] to 'Elixir.Mint.HTTP':connect/4. This avoids the vulnerable HTTP/2 receive path entirely, at the cost of losing HTTP/2 for those connections.
Resources
Impact
Remote, unauthenticated denial-of-service against any process using Mint as an HTTP/2 client against an untrusted or attacker-influenced server. A single connection is sufficient to drive memory to arbitrary size and crash the BEAM process. The default Mint configuration is vulnerable; no client-side opt-in is required. Scored CVSS v4.0 8.2 (HIGH).
The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-49754? CVE-2026-49754 is a high-severity allocation of resources without limits or throttling vulnerability in mint (erlang), affecting versions < 1.9.0. It is fixed in 1.9.0. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
- Which versions of mint are affected by CVE-2026-49754? mint (erlang) versions < 1.9.0 is affected.
- Is there a fix for CVE-2026-49754? Yes. CVE-2026-49754 is fixed in 1.9.0. Upgrade to this version or later.
- Is CVE-2026-49754 exploitable, and should I be worried? Whether CVE-2026-49754 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-49754 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-49754? Upgrade
mintto 1.9.0 or later.