Slack Morphism verifier errors disclose valid HMACs in the logs

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-113799
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-21 17:18:25 UTC
Updated2026-10-21 17:18:25 UTC
DescriptionSlack 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.

Risk And Classification

Primary CVSS: v3.1 5.3 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N

Problem Types: CWE-532 | CWE-532 CWE-532: Insertion of Sensitive Information into Log File

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.3MEDIUMCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N
3.1CNADECLARED5.3MEDIUMCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Abdolence Slack-morphism-rust affected >= 1.0.0, < 2.28.0 Not specified

References

ReferenceSourceLinkTags
github.com/abdolence/slack-morphism-rust/pull/387 [email protected] github.com
github.com/abdolence/slack-morphism-rust/commit/ac95d0d4539d0eac548a8db9... [email protected] github.com
github.com/abdolence/slack-morphism-rust/releases/tag/v2.28.0 [email protected] github.com
github.com/abdolence/slack-morphism-rust/security/advisories/GHSA-26w4-8... [email protected] github.com
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