# Hysteria: http large header with sniff cause server DoS

Advisory record · `GHSA-jqc5-2p7q-fqfc`

- **Identifiers:** `GHSA-jqc5-2p7q-fqfc` · `GO-2026-5813`
- **State:** Confirmed
- **Severity:** CVSS 7.5 High
- **Critical:** No
- **Weakness (CWE):** [CWE-770](https://cwe.mitre.org/data/definitions/770.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md)
- **Published:** 26 Jun 2026
- **Updated:** 7 Jul 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 26 Jun 2026, 20:19 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `github.com/apernet/hysteria` (Go): affected `<2.9.2`; fixed in `2.9.2`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Hysteria (Go package github.com/apernet/hysteria) versions before 2.9.2 are vulnerable to a denial of service caused by excessively large HTTP headers during traffic sniffing. A remote attacker who can reach the server can send headers without the end-of-header marker, causing the server to consume large amounts of memory, reportedly up to 16GB in testing, and possibly run out of memory. Upgrade to version 2.9.2 or later.

Written 6 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 7.5 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`, from GitHub Advisory Database

- **CISA KEV:** Not listed.
- **EPSS:** No score.

## Timeline

- 31 Oct 2026, 15:05 UTC: First seen by agentprime
- 31 Oct 2026, 15:05 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-jqc5-2p7q-fqfc)

## Sources

- [GitHub Advisory Database: GHSA-jqc5-2p7q-fqfc](https://github.com/advisories/GHSA-jqc5-2p7q-fqfc)
- [OSV: GHSA-jqc5-2p7q-fqfc](https://osv.dev/vulnerability/GHSA-jqc5-2p7q-fqfc)
- <https://github.com/apernet/hysteria/security/advisories/GHSA-jqc5-2p7q-fqfc>
- <https://github.com/apernet/hysteria>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-jqc5-2p7q-fqfc>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-jqc5-2p7q-fqfc/>. Everything for agents: <https://agentprime.io/llms.txt>.