GHSA-GXHX-2686-5H9G

Vulnerability from github – Published: 2026-05-14 20:52 – Updated: 2026-06-29 15:38
VLAI
Summary
slack-go `SecretsVerifier` accepts empty signing secret without precondition
Details

SecretsVerifier in slack-go/slack before v0.23.1 accepts an empty signing secret without error. If an application is misconfigured (e.g., an unset or empty SLACK_SIGNING_SECRET), NewSecretsVerifier builds an HMAC-SHA256 keyed with an empty string, allowing an unauthenticated attacker to forge a valid X-Slack-Signature and bypass Slack request authentication. Fixed in v0.23.1, which rejects empty secrets with ErrInvalidConfiguration. This is patched in version 0.23.1.

Severity
4.8 (Medium)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N/E:U
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/slack-go/slack"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.23.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-1391",
      "CWE-287",
      "CWE-326"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-14T20:52:55Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "`SecretsVerifier` in slack-go/slack before v0.23.1 accepts an empty signing secret without error. If an application is misconfigured (e.g., an unset or empty `SLACK_SIGNING_SECRET`), `NewSecretsVerifier` builds an HMAC-SHA256 keyed with an empty string, allowing an unauthenticated attacker to forge a valid `X-Slack-Signature` and bypass Slack request authentication. Fixed in v0.23.1, which rejects empty secrets with `ErrInvalidConfiguration`. This is patched in version 0.23.1.",
  "id": "GHSA-gxhx-2686-5h9g",
  "modified": "2026-06-29T15:38:00Z",
  "published": "2026-05-14T20:52:55Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/slack-go/slack/security/advisories/GHSA-gxhx-2686-5h9g"
    },
    {
      "type": "WEB",
      "url": "https://github.com/slack-go/slack/commit/34ad5c052e446f58505ae8d81a2a72821de107cc"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/slack-go/slack"
    },
    {
      "type": "WEB",
      "url": "https://github.com/slack-go/slack/releases/tag/v0.23.1"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N/E:U",
      "type": "CVSS_V4"
    }
  ],
  "summary": "slack-go `SecretsVerifier` accepts empty signing secret without precondition"
}



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