# ex-aws ex_aws_sns signature bypass via untrusted SigningCertURL

Source: https://junglewise.ai/threats/ex-aws-ex-aws-sns-signature-bypass-via-untrusted-signingcerturl-0591112d  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-26. Updated: 2026-06-26  
License: CC BY 4.0 with a link back

Severity: high · CVSS 8.7 · Published 2026-06-26

A security vulnerability in the ex_aws_sns library allows attackers to bypass signature verification for Amazon Simple Notification Service (SNS) messages. This library is used by Elixir applications to interact with AWS SNS, and an exploit could allow an unauthorized person to send fake notifications that the system treats as legitimate. This could lead to unauthorized data processing, hijacking of message delivery, or disruption of legitimate service subscriptions.

Vendors: [Erlang](https://junglewise.ai/threats/vendors/erlang).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** High severity, with a CVSS score of 8.7, published 26 June 2026.

**Which products and versions are affected?** Erlang Ex Aws Sns >= 2.0.1, < 2.3.5; ExAws.SNS >= 2.0.1, < 2.3.5.

**Is there a fix for This vulnerability?** A patch was published on 2026-05-28: Remediation developed and published to repository Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network, in a software library.

**Am I affected?** Check whether you run Erlang Ex Aws Sns or ExAws.SNS 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.

## Technical details

The `ExAws.SNS.verify_message/1` function in `ex_aws_sns` versions 2.0.1 through 2.3.4 fetches the signing certificate from the `SigningCertURL` field of an incoming SNS message without validating the URL's protocol or hostname. An unauthenticated attacker can provide a URL pointing to a malicious certificate they control. Because the library uses this untrusted certificate to verify the message's RSA signature, the attacker can successfully sign forged SNS payloads. This allows for the spoofing of Notification, SubscriptionConfirmation, and UnsubscribeConfirmation messages. The issue is fixed in version 2.3.5 by enforcing HTTPS and validating that the certificate host belongs to an AWS-owned SNS domain.

## Affected products

- ex-aws ex_aws_sns >= 2.0.1, < 2.3.5

## Timeline

- 2026-05-28: patched: Remediation developed and published to repository
- 2026-06-26: advisory: GitHub Advisory published

## References

- [https://api.github.com/users/PJUllrich](https://api.github.com/users/PJUllrich)
- [https://github.com/PJUllrich](https://github.com/PJUllrich)
- [https://api.github.com/users/PJUllrich/gists%7B/gist_id%7D](https://api.github.com/users/PJUllrich/gists%7B/gist_id%7D)
- [https://api.github.com/users/PJUllrich/repos](https://api.github.com/users/PJUllrich/repos)
- [https://avatars.githubusercontent.com/u/10426523?v=4](https://avatars.githubusercontent.com/u/10426523?v=4)
- [https://api.github.com/users/PJUllrich/events%7B/privacy%7D](https://api.github.com/users/PJUllrich/events%7B/privacy%7D)

## Related threats

- [ex-aws ex_aws_sns signature bypass in verify_message/1](https://junglewise.ai/threats/cve-2026-47074-ex-aws-ex-aws-sns-signature-bypass-in-verify-message-1)