# CVE-2026-113799: Slack Morphism signature disclosure in error logging

Source: https://junglewise.ai/threats/cve-2026-113799-slack-morphism-verifier-errors-disclose-valid-hmacs-in-the-logs  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-21. Updated: 2026-10-21  
License: CC BY 4.0 with a link back

CVE-2026-113799 · Severity: medium · CVSS 5.3 · Published 2026-10-21

Slack Morphism is a client library that validates incoming requests from Slack by verifying cryptographic signatures. Versions 1.0.0 through 2.27.0 leak the correct signature in error logs when signature verification fails, allowing an attacker who can read application logs to forge valid Slack requests and bypass authentication to the application's callback endpoints.

Technologies: [slack-morphism (crates.io)](https://junglewise.ai/threats/technologies/slack-morphism). Vendors: [crates.io](https://junglewise.ai/threats/vendors/crates-io).

## Quick answers

**Is CVE-2026-113799 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-113799 being exploited in the wild.

**How severe is CVE-2026-113799?** Medium severity, with a CVSS score of 5.3, published 21 October 2026.

**Which products and versions are affected?** Abdolence Slack Morphism 1.0.0 through 2.27.0; slack-morphism (crates.io) >= 1.0.0, <= 2.27.0, SEMVER:introduced=1.0.0,fixed=2.28.0; Slack Morphism project Slack-Morphism 2.26.0 through 2.27.0; likely all versions from 0.10.0 onward based on git history.

**Is there a fix for CVE-2026-113799?** Yes. slack-morphism (crates.io): upgrade to 2.28.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-113799 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-113799?** Check whether you run Abdolence Slack Morphism, slack-morphism (crates.io) or Slack Morphism project Slack-Morphism at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- slack-morphism (crates.io): upgrade to 2.28.0 or later

  ```sh
  cargo update -p slack-morphism
  ```


## Technical details

The vulnerability exists in the SlackEventWrongSignatureError exception handler, which exposes the computed correct HMAC signature in its Debug and Display representations. An attacker can send a request with an invalid signature, retrieve the correct signature from application error logs, and replay the same request within the five-minute freshness window to pass verification without knowing the Slack signing secret. This requires network access to the callback endpoint and read access to application logs.

## Affected products

- abdolence Slack Morphism 1.0.0 through 2.27.0

## Identifiers

- CVE-2026-113799
- GHSA-26w4-8w32-4x3v

## Timeline

- 2026-10-21: disclosed
- 2026-09-09: patched

## References

- [https://github.com/abdolence/slack-morphism-rust/commit/ac95d0d4539d0eac548a8db99c51c0c1ae832756](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/pull/387)

## Related threats

- [RUSTSEC-2022-0087 - Slack Webhooks secrets leak in debug logs](https://junglewise.ai/threats/cve-2022-39292-exposure-of-sensitive-slack-webhook-urls-in-debug-logs-and-traces)
- [RUSTSEC-2022-0086 - Slack OAuth Secrets leak in debug logs](https://junglewise.ai/threats/cve-2022-31162-slack-morphism-for-rust-before-0-41-0-can-leak-slack-oauth-client)