GHSA-QH5X-RFWF-RVFV is a high-severity allocation of resources without limits or throttling vulnerability in github.com/apernet/hysteria (go), affecting versions < 2.9.2. It is fixed in 2.9.2.
Summary An authenticated client can crash the Hysteria server by advertising a very small QUIC maxdatagramframesize and then triggering a UDP response from the server. When the server tries to send the UDP response back via QUIC DATAGRAM, quic-go returns DatagramTooLargeError. The server then attempts to fragment the Hysteria UDP message, but the fragmentation code does not handle the case where the UDP message header itself is larger than the maximum datagram payload size. This results in a slice bounds panic and terminates the server process. Details The vulnerable path is the normal server-side UDP response path: In core/server/udp.go, receiveLoop packages a UDP response into a protocol.UDPMessage and calls sendMessageAutoFrag. If SendDatagram fails with quic.DatagramTooLargeError, sendMessageAutoFrag calls: However, FragUDPMessage in core/internal/frag/frag.go assumes that maxSize is greater than the UDP message header size: If an attacker-controlled client advertises a small enough maxdatagramframesize, errTooLarge.MaxDatagramPayloadSize can be smaller than m.HeaderSize(). In that case, maxPayloadSize becomes zero or negative, and the later slicing operation panics: PoC poc.yaml poc.go poc.sh Impact Server crash
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-QH5X-RFWF-RVFV 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 (2.9.2). Upgrading removes the vulnerable code path.
go
github.com/apernet/hysteria (< 2.9.2)github.com/apernet/hysteria → 2.9.2 (go)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.
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Already deployed Kodem? See GHSA-QH5X-RFWF-RVFV in your environment →Upgrade github.com/apernet/hysteria to 2.9.2 or later to resolve this vulnerability.
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GHSA-QH5X-RFWF-RVFV is a high-severity allocation of resources without limits or throttling vulnerability in github.com/apernet/hysteria (go), affecting versions < 2.9.2. It is fixed in 2.9.2. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
GHSA-QH5X-RFWF-RVFV 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.
github.com/apernet/hysteria (go) versions < 2.9.2 is affected.
Yes. GHSA-QH5X-RFWF-RVFV is fixed in 2.9.2. Upgrade to this version or later.
Whether GHSA-QH5X-RFWF-RVFV 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
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.
Upgrade github.com/apernet/hysteria to 2.9.2 or later.