CVE-2026-47074

## Duplicate Advisory This advisory has been withdrawn because it is a duplicate of GHSA-jq4m-q6p2-8gwc. This link is maintained to preserve external references. ## Original Description Allocation of Resources Without Limits or Throttling vulnerability in benoitc hackney allows Flooding. hackney_h3:await_response_loop/6 accumulates the HTTP/3 response body in memory without any size cap. The after Timeout clause is a per-message inactivity timer that resets on every received chunk, housekeeping message, or settings frame — it is not a wall-clock deadline. A malicious HTTP/3 server that emits one small chunk every Timeout - 1 ms with Fin = false and never sends a final frame keeps the loop alive indefinitely while the accumulation buffer grows linearly without bound, eventually exhausting the BEAM process heap and causing an out-of-memory condition. This issue affects hackney: from 2.0.0 before 4.0.1.

### Summary `ExAws.SNS.verify_message/1` fetches the signing certificate from the `SigningCertURL` field of the incoming SNS message without validating that the URL uses HTTPS or that its host is an AWS-owned SNS certificate domain. An unauthenticated attacker who can POST to any endpoint that calls `verify_message/1` can supply an attacker-controlled `SigningCertURL`, sign a forged SNS message with their own RSA key, and cause the function to return `:ok`, completely bypassing SNS signature verification. ### Details In `lib/ex_aws/sns.ex` (lines 475–483), `verify_message/1` performs three checks: `validate_message_params/1` (confirms required fields are present), `validate_signature_version/1` (confirms `SignatureVersion == "1"`), then signature verification. The signature step calls `ExAws.SNS.PublicKeyCache.get(message["SigningCertURL"])` and passes the result to `:public_key.verify/4`. Neither `validate_message_params/1` nor any other step checks that `SigningCertURL` is an HTTPS URL or that the hostname matches the expected pattern (e.g. `sns.<region>.amazonaws.com`). `PublicKeyCache.get/1` in `lib/ex_aws/sns/public_key_cache.ex` fetches whatever URL is provided and caches the certificate. The RSA signature then verifies against the attacker's own public key, and `verify_message/1` returns `:ok`. ### PoC 1. Generate an RSA keypair and host the DER/PEM public certificate at any URL reachable from the target server (e.g. `http://attacker.example/cert.pem`). 2. Build a forged `Notification` payload with an arbitrary `TopicArn` and `Message`, compute the canonical string-to-sign per the SNS spec, and sign it with the attacker private key. 3. Set `SigningCertURL` to the attacker URL and `Signature` to the base64-encoded signature. 4. POST the forged payload to any SNS webhook endpoint that calls `ExAws.SNS.verify_message/1`. 5. The function returns `:ok`; the application treats the message as authentic. ### Configurations The application must expose an HTTP endpoint that calls `ExAws.SNS.verify_message/1` on incoming request bodies (the standard SNS webhook pattern). ### Impact Complete SNS signature authentication bypass. Affects `ex_aws_sns` from 2.0.1 through 2.3.4. Consequences include spoofing arbitrary `Notification` payloads, auto-confirming attacker-controlled `SubscribeURL` values to hijack topic delivery, and spoofing `UnsubscribeConfirmation` to disrupt legitimate subscriptions. No authentication or special configuration on the attacker side is required. CVSS v4.0: **8.7 (HIGH)**. ## Resources * Introduction commit: https://github.com/ex-aws/ex_aws_sns/commit/a7ec21880943f4dac1d59bda557db0ffcd2b61fa * Patch commit: https://github.com/ex-aws/ex_aws_sns/commit/1853d280b152d10384a1e21a22cf22152a60be48

## Summary Improper Certificate Validation vulnerability in ex-aws ex\_aws\_sns (ExAws.SNS, ExAws.SNS.PublicKeyCache modules) allows Signature Spoofing by Improper Validation. This vulnerability is associated with program files lib/ex\_aws/sns.ex, lib/ex\_aws/sns/public\_key\_cache.ex and program routines 'Elixir.ExAws.SNS':verify\_message/1, 'Elixir.ExAws.SNS.PublicKeyCache':get/1. 'Elixir.ExAws.SNS':verify\_message/1 fetches the signing certificate from the SigningCertURL field of the incoming SNS message without validating that the URL uses HTTPS or that the host matches an AWS-owned SNS certificate domain. An unauthenticated attacker who can POST to an endpoint that calls verify\_message/1 can supply an attacker-controlled SigningCertURL, sign a forged SNS message with their own key, and cause the function to return :ok, completely bypassing SNS signature verification. This issue affects ex\_aws\_sns: from 2.0.1 before 2.3.5. ## Configurations The application must expose an HTTP endpoint that calls 'Elixir.ExAws.SNS':verify\_message/1 on incoming request bodies.