{"cve":"CVE-2026-113799","nvd":{"published":"2026-10-21T17:18:25.123","modified":"2026-10-22T17:40:46.877","status":"Deferred","description":"Slack Morphism is a client library for Slack Web/Events API/Socket Mode and Block Kit. Versions 1.0.0 through 2.27.0 expose the correct Slack request HMAC when signature verification fails. For an invalid request, `slack-morphism` computes the correct signature for the attacker-controlled timestamp and request body and stores it in `SlackEventWrongSignatureError.generated_hash`. The error's `Debug` and `Display` representations expose that value, and the default Axum listener error handler logs it at error level. An attacker who can both reach the application's Slack callback endpoint and read its application/service logs can therefore use the verifier as a chosen-message HMAC oracle. The attacker can send an arbitrary request with an invalid signature, recover the correct signature from the resulting log entry, and resend the same request within the five-minute freshness window. The second request passes Slack Morphism's signature verification and reaches the protected application callback without the attacker knowing the Slack signing secret. Version 2.28.0 patches the issue.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N","score":5.3},"cwes":["CWE-532"],"references":["https://github.com/abdolence/slack-morphism-rust/commit/ac95d0d4539d0eac548a8db99c51c0c1ae832756","https://github.com/abdolence/slack-morphism-rust/pull/387","https://github.com/abdolence/slack-morphism-rust/releases/tag/v2.28.0","https://github.com/abdolence/slack-morphism-rust/security/advisories/GHSA-26w4-8w32-4x3v"],"products":[],"source":"nvd","synced_at":"2026-10-23T16:39:26.291718493+00:00"},"epss":{"cve":"CVE-2026-113799","score":0.00384,"percentile":0.32167,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-26w4-8w32-4x3v","url":"https://osv.dev/vulnerability/GHSA-26w4-8w32-4x3v","summary":"Slack Morphism verifier errors disclose valid HMACs in the logs","modified":"2026-10-21T16:45:04.128108390Z","packages":[{"ecosystem":"crates.io","name":"slack-morphism","purl":"pkg:cargo/slack-morphism","ranges":[">=1.0.0 <2.28.0"],"fixed":["2.28.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}