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ETK-2026-625

ETK-2026-625Zero's internal tracking ID, independent of the CVE number.

validatedZero produced an exploit or a check.

GHSA-7rj2-5w9w-r9jx ↗

check availableZero validated a working check for it.not proven exploitableZero has a detection check, but hasn't produced a full working exploit yet.
awaiting cvepublic pocExploit code has been published by someone. Source signals can also carry a PoC (Proof of Concept).−17dkevAttacks confirmed in the real world.
nuget:MessagePack [; 2.5.307); [3.0; 3.1.11)
fixed in 2.5.307, 3.1.11
CWE-190 Integer Overflow or Wraparound
ETK-2026-625, no cve assigned
pkg:nuget/MessagePack
cvss7.5cna vendorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
−16dTTV
14mAI analysisAnalysis: how long the AI spent reversing this signal.
Check if you are vulnerable
timeline
0 = trigger signal
trigger signal +0dpublic poc+0dcheck available+1.3dagent stopped
0
+5d
+10d
+15d

description

The MessagePack NuGet package can overflow an integer while decompressing LZ4-compressed MessagePack input, leading to an out-of-bounds memory access and process termination. An attacker needs to send MessagePack data to an application that deserializes untrusted input with Lz4Block or Lz4BlockArray compression enabled.

mitigation

Upgrade MessagePack to 2.5.307, 3.1.11 or later.

fixed in 2.5.307, 3.1.11

check
available
exploit
no
automationDeterministic: a check that runs on its own, the same request on every target. Contextual: an agentic technique that needs to be applied per target, for bugs that depend on contextual flows.
contextual
auth requiredWhether an attacker needs an account first, based on the CVSS vector's Privileges Required.
no
EPSSEstimate of the chance this CVE is exploited in the next 30 days. Refreshed daily.
–
agent run time
14m
cve.org record, t = 0The moment cve.org publishes the CVE in full.
not published yet
Δ to public pocExploit code has been published by someone. Source signals can also carry a PoC (Proof of Concept).
−17d
Δ to kevAttacks confirmed in the real world.
–

outcome

Mechanism verified: the exploit fired on the vulnerable build and stayed silent on the patched one, but the server it ran against was ours, so no check ships for it.

source signals

Public signals that triggered or updated the pipeline. These are inputs for the deltas above.

  1. 2026-10-03 22:28Z
  2. 2026-10-03 22:28Z

this entry in the feed

GET /api/v1/feed/ETK-2026-625

{
  "etk_id": "ETK-2026-625",
  "cve_id": null,
  "display_id": "ETK-2026-625",
  "ghsa_id": "GHSA-7rj2-5w9w-r9jx",
  "euvd_id": null,
  "status": "published",
  "anchor_state": "awaiting_cve",
  "title": "Integer overflow in MessagePack LZ4 decompression",
  "summary": "The MessagePack NuGet package can overflow an integer while decompressing LZ4-compressed MessagePack input, leading to an out-of-bounds memory access and process termination. An attacker needs to send MessagePack data to an application that deserializes untrusted input with Lz4Block or Lz4BlockArray compression enabled.",
  "mitigation": "Upgrade MessagePack to 2.5.307, 3.1.11 or later.",
  "vendor": "nuget",
  "product": "nuget:MessagePack",
  "affected": [
    {
      "affected_notes": [
        "[",
        "2.5.307)",
        "[3.0",
        "3.1.11)"
      ],
      "affected_ranges": [],
      "ecosystem": "nuget",
      "fixed_versions": [
        "2.5.307",
        "3.1.11"
      ],
      "package_name": "MessagePack",
      "purl": "pkg:nuget/MessagePack"
    }
  ],
  "cwes": [
    190
  ],
  "cvss_score": 7.5,
  "cvss_src": "cna_vendor",
  "cvss_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
  "epss_score": null,
  "epss_percentile": null,
  "epss_asof": null,
  "automation": "contextual",
  "check": true,
  "check_confidence_basis": "mechanism_verified",
  "exploit": false,
  "pipeline_minutes": 14.237647666666666,
  "t0_at": null,
  "signals": {
    "check": {
      "at": "2026-10-05T06:35:07.482272+00:00",
      "days": -16.05755865872685,
      "is_lower_bound": true,
      "measured_at": "2026-10-21T07:58:00.572652+00:00",
      "url": null
    },
    "public_poc": {
      "at": "2026-10-03T22:28:02+00:00",
      "days": -17.39581655539352,
      "is_lower_bound": true,
      "measured_at": "2026-10-21T07:58:00.572652+00:00",
      "url": "https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-7rj2-5w9w-r9jx"
    },
    "trigger_signal": {
      "at": "2026-10-03T22:28:02+00:00",
      "days": -17.39581655539352,
      "is_lower_bound": true,
      "measured_at": "2026-10-21T07:58:00.572652+00:00",
      "url": "https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-7rj2-5w9w-r9jx"
    }
  }
}

published 2026-10-05 06:20Z
last change 2026-10-21 07:48Z

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