Summary
Yamux Memory Exhaustion Vulnerability via Active::pending_frames property
Attack scenario
The Rust implementation of the Yamux stream multiplexer uses a vector for pending frames. This vector is not bounded in length. Every time the Yamux protocol requires sending of a new frame, this frame gets appended to this vector. This can be remotely triggered in a number of ways, for example by:
- Opening a new libp2p Identify stream. This causes the node to send its Identify message. Of course, every other protocol that causes the sending of data also works. The larger the response, the more data is enqueued.
- Sending a Yamux Ping frame. This causes a Pong frame to be enqueued.
Under normal circumstances, this queue of pending frames would be drained once they’re sent out over the network. However, the attacker can use TCP’s receive window mechanism to prevent the victim from sending out any data: By not reading from the TCP connection, the receive window will never be increased, and the victim won’t be able to send out any new data (this is how TCP implements backpressure). Once this happens, Yamux’s queue of pending frames will start growing indefinitely. The queue will only be drained once the underlying TCP connection is closed.
Components
https://github.com/libp2p/rust-yamux/blob/yamux-v0.13.1/yamux/src/connection.rs#L289
Details
This attack is inspired by the HTTP/2 Rapid Reset Attack (CVE 2023-44487), HTTP/2 Ping Flood (CVE-2019-9512), and the QUIC Path Validation attack (see my blog post: https://seemann.io/posts/2023-12-18-exploiting-quics-path-validation/).
Impact
An attacker can cause a remote node to run out of memory, which will result in the corresponding process getting terminated by the operating system.
Depending on the application protocols running on top of rust-libp2p, higher amplification factors are possible. For example, image a protocol that sends out 10 MB of data as a result of an incoming request. By issuing that request and sending a Yamux stream window update (together ~100-200 bytes), the victim would now enqueue the entire 10 MB into its frame buffer. Any block transfer / sync protocols might be good candidates.
In addition to consuming huge amounts of memory, this attack also drives up the victim's CPU load, such that the allocation of memory at some point becomes CPU-limited.
This was originally submitted by @marteen-seemann to the Ethereum Foundation bug bounty program.
Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.
CVE-2024-32984 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.13.2); upgrading removes the vulnerable code path.
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-2024-32984? CVE-2024-32984 is a high-severity uncontrolled resource consumption vulnerability in yamux (rust), affecting versions >= 0.13.0, < 0.13.2. It is fixed in 0.13.2. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
- How severe is CVE-2024-32984? CVE-2024-32984 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of yamux are affected by CVE-2024-32984? yamux (rust) versions >= 0.13.0, < 0.13.2 is affected.
- Is there a fix for CVE-2024-32984? Yes. CVE-2024-32984 is fixed in 0.13.2. Upgrade to this version or later.
- Is CVE-2024-32984 exploitable, and should I be worried? Whether CVE-2024-32984 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-2024-32984 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-2024-32984? Upgrade
yamuxto 0.13.2 or later.