Summary
Rustls: Brotli certificate decompression can allocate an attacker-controlled amount of memory up to 1 GiB before authentication.
The built-in (but disabled by default) Brotli certificate decoder bounds the output buffer but accepts an input-selected history window. A header of five bytes can specify a 1 GiB window allocation. A peer can abort a process whose allocator cannot satisfy that request. A client must enable Brotli and connect to the peer; a server must enable Brotli and request a client certificate. Neither direction requires a trusted attacker certificate.
Details
rustls calls BrotliDecompress which enables Brotli's large-window extension. rustls applies a limit to certificates, but this applies to the decompressed result, and not to any internal allocations the process requires.
Acknowledgement
Thanks to OpenAI [email protected] for the disclosure.
Impact
Client applications that enable the brotli feature will be vulnerable to malicious servers. Server applications that enable the brotli feature and enable client authentication will be vulnerable to malicious clients.
Potential for denial of service due to memory exhaustion from peers sending malicious Brotli-encoded certificates, for applications that enable Brotli decompression.
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.
GHSA-H2V8-394M-P7VV has a CVSS score of 3.7 (Low). 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 (0.23.46, 0.24.0-dev.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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rustls to 0.23.46 or later; rustls to 0.24.0-dev.2 or later
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Frequently Asked Questions
- What is GHSA-H2V8-394M-P7VV? GHSA-H2V8-394M-P7VV is a low-severity allocation of resources without limits or throttling vulnerability in rustls (rust), affecting versions < 0.23.46. It is fixed in 0.23.46, 0.24.0-dev.2. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
- How severe is GHSA-H2V8-394M-P7VV? GHSA-H2V8-394M-P7VV has a CVSS score of 3.7 (Low). 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 rustls are affected by GHSA-H2V8-394M-P7VV? rustls (rust) versions < 0.23.46 is affected.
- Is there a fix for GHSA-H2V8-394M-P7VV? Yes. GHSA-H2V8-394M-P7VV is fixed in 0.23.46, 0.24.0-dev.2. Upgrade to this version or later.
- Is GHSA-H2V8-394M-P7VV exploitable, and should I be worried? Whether GHSA-H2V8-394M-P7VV 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 GHSA-H2V8-394M-P7VV 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 GHSA-H2V8-394M-P7VV?
- Upgrade
rustlsto 0.23.46 or later - Upgrade
rustlsto 0.24.0-dev.2 or later
- Upgrade