CVE-2026-34219: libp2p-gossipsub Remote Crash Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-xqmp-fxgv-xvq5",
  "modified" : "2026-04-06T23:13:23Z",
  "published" : "2026-03-30T13:04:03Z",
  "aliases" : [ "CVE-2026-34219" ],
  "summary" : "libp2p-gossipsub: Remote crash via unchecked Instant overflow in heartbeat backoff expiry handling",
  "details" : "## Description\n### Summary\nThe Rust libp2p Gossipsub implementation contains a remotely reachable panic in `backoff` expiry handling.  \nAfter a peer sends a crafted `PRUNE` control message with an attacker-controlled, near-maximum `backoff` value, the value is accepted and stored as an `Instant` near the representable upper bound. On a later heartbeat, the implementation performs unchecked `Instant + Duration` arithmetic (`backoff_time + slack`), which can overflow and panic with:\n`overflow when adding duration to instant`\nThis issue is reachable from any Gossipsub peer over normal `TCP + Noise + mplex/yamux` connectivity and requires no further authentication beyond becoming a protocol peer.\n### Attack Scenario\nAn attacker that can establish a libp2p Gossipsub session with a target node can crash the target by sending crafted `PRUNE` control data:\n1. Establish a standard libp2p session (`TCP + Noise`) and negotiate a stream multiplexer (`mplex`/`yamux`).\n2. Open a Gossipsub stream and send an RPC containing `ControlPrune` with a very large `backoff` (chosen near boundary conditions, e.g. `~ i64::MAX - victim_uptime_seconds`; example observed: `9223372036854674580` for ~28h uptime).\n3. The value is parsed from protobuf and passed through `Behaviour::handle_prune()` into mesh/backoff update logic.\n4. Initial storage path uses checked addition (`Instant::now().checked_add(...)`), so the malicious near-max value is retained.\n5. On the next heartbeat (typically within ~43–74s), expiry logic computes `backoff_time + slack` using unchecked addition, which overflows and panics.\n### Impact\nRemote unauthenticated denial of service (critical).  \nAny application exposing an affected `libp2p-gossipsub` listener can be crashed by a network-reachable peer that sends crafted `PRUNE` backoff values. The crash is triggered during heartbeat processing (not immediately at PRUNE parse time), and can be repeated by reconnecting and replaying the message.\n\n### Differences from CVE-2026-33040\nThis advisory is related to CVE-2026-33040 but it is not the same defect. CVE-2026-33040 addressed overflow during backoff insertion by adding checked arithmetic when converting PRUNE backoff into an Instant. The issue in this advisory occurs at a different location and at a different time: a near-maximum backoff can still be stored successfully, and the crash happens later in the heartbeat path when slack is added to that stored Instant using unchecked arithmetic.  This report covers a distinct secondary overflow path in heartbeat expiry handling that remained reachable after the original insertion-side hardening.\n\nThis vulnerability was originally reported by the Security team of the Ethereum Foundation.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "libp2p-gossipsub"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.49.4"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/libp2p/rust-libp2p/security/advisories/GHSA-xqmp-fxgv-xvq5"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-34219"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-gc42-3jg7-rxr2"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/libp2p/rust-libp2p"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-190", "CWE-617" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-30T13:04:03Z",
    "nvd_published_at" : "2026-03-31T16:16:31Z"
  }
}