---
id: "CVE-2026-123096"
kind: "vulnerability"
aliases: ["CVE-2026-123096"]
title: "anacrolix/torrent: unbounded tracker responses let malicious trackers crash clients"
severity: "high"
cvss: 7.1
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["bittorrent", "go", "package", "torrent-clients"]
not_affected_if: ["no-untrusted-torrents", "udp-trackers-only"]
published_at: "2026-11-05T16:17:46+00:00"
first_seen_at: "2026-11-05T16:40:02+00:00"
updated_at: "2026-11-05T16:41:37+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-123096", "first_seen_at": "2026-11-05T16:40:02+00:00"}]
exploit_sources: []
---

# anacrolix/torrent: unbounded tracker responses let malicious trackers crash clients

The anacrolix/torrent Go library reads HTTP tracker announce and scrape responses into memory without a size limit. A malicious tracker can return huge or gzip-compressed responses to exhaust the client process's memory and crash it.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check whether the application imports `github.com/anacrolix/torrent` at a version through `1.61.0` in `go.mod`.
- Check whether the code calls `Client.Announce` or `Client.Scrape` against HTTP trackers taken from untrusted torrent files or magnet links.

## Fix

- `github.com/anacrolix/torrent`: a patch is linked in the sources, but the fixed version is not stated.

## Timeline

- 2026-11-05T16:40:02+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-123096

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/anacrolix-torrent-through-1.61.0-memory-exhaustion-via-unbounded-http-tracker-response
- [fix] Patch: github.com https://github.com/anacrolix/torrent/commit/92ad51490479bb8b94720f964b1c67e5a1d68faa

## From the sources

anacrolix/torrent through 1.61.0 contains a memory exhaustion vulnerability in the tracker/http package that allows malicious trackers to crash clients by returning unbounded responses. Attackers controlling an HTTP tracker in a torrent file or magnet link can return huge or gzip-compressed announce or scrape responses that Client.Announce and Client.Scrape buffer without limits, exhausting process memory.

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