[BUG]: 4.12.0 breaks AWS Secrets Manager #19358

Tracer Version(s)

4.12.0

Python Version(s)

Python 3.10.12

Pip Version(s)

26.1.2

Bug Report

After updating to 4.12.0, requests to Secrets Manager result in an exception.

Reproduction Code

secrets_manager = boto3.client(
    'secretsmanager',
    region_name='eu-west-1',
)
secretv_value = secrets_manager.get_secret_value(SecretId='some_secret')['SecretString']

Error Logs

ClientError: An error occurred (InvalidSignatureException) when calling the GetSecretValue operation: The request signature we calculated does not match the signature you provided. Check your AWS Secret Access Key and signing method. Consult the service documentation for details.

The Canonical String for this request should have been
'POST
/

baggage:REDACTED
content-type:application/x-amz-json-1.1
host:secretsmanager.eu-west-1.amazonaws.com
traceparent:00-46e0bbc8e16611d51e02b7734d5b9164-c94a73ad0dd252f4-01
tracestate:dd=p:c94a73ad0dd252f4;s:1;t.tid:46e0bbc8e16611d5
x-amz-date:20260729T085146Z
x-amz-security-token:REDACTED
x-amz-target:secretsmanager.GetSecretValue
x-datadog-parent-id:14504532736998527732
x-datadog-sampling-priority:1
x-datadog-tags:_dd.p.tid=46e0bbc8e16611d5
x-datadog-trace-id:2162492476938228068

baggage;content-type;host;traceparent;tracestate;x-amz-date;x-amz-security-token;x-amz-target;x-datadog-parent-id;x-datadog-sampling-priority;x-datadog-tags;x-datadog-trace-id
e6a334aa48ab1c2844e3c47c540a753ec87a6d038dc58e1493c3e94029bee344'

The String-to-Sign should have been
'AWS4-HMAC-SHA256
20260729T085146Z
20260729/eu-west-1/secretsmanager/aws4_request
d36145e21b79f2911f673664f893b1119fb9003935ddcccb1cc1bc99e255c816'

Libraries in Use

No response

Operating System

Linux ip-10-10-35-235 6.8.0-1061-aws #64~22.04.1-Ubuntu SMP Thu Jul 16 14:38:59 UTC 2026 x86_64 x86_64 x86_64 GNU/Linux