Legacy `azure_core` writes the `authorization` header value to logs

Applications built on the legacy Azure SDK for Rust (`azure_core` 0.21.0 and
earlier) write the value of the outgoing `authorization` header to their logs
whenever debug-level logging is enabled, and in every affected version also at
trace level. The leaked values are live credentials — Microsoft Entra
ID bearer tokens, Azure Storage SharedKey signatures, and SAS tokens — and
anyone with read access to the logs can replay them until they expire
(CWE-532).

Versions 0.22.0 and later, which are the rewritten and currently supported
SDK, do not contain the affected code.

## Affected versions

Every published legacy version except 0.2.0 writes the `authorization` header
value to logs: 0.1.1 (2022-01-25), and 0.2.1 through 0.21.0 (2024-10-15).

## Mitigation

- Upgrade to `azure_core` 1.0.0 or newer.
- If you are unable to upgrade, raise the log level above debug for the
impacted crates or submit a feature request for missing crates built on `azure_core` 1.0.0 or newer.
- Treat logs produced by an affected build as credential-bearing: rotate any
long-lived secret that authenticated a request while debug logging was on.

## Coordination

The finding was reported to the Microsoft Security Response Center
(VULN-211331), which determined that it does not meet the Microsoft Security
Servicing Criteria definition of a security vulnerability.

It was then disclosed publicly as [Azure/azure-sdk-for-rust#5074][issue] on
2026-08-15, asking the maintainers to confirm the behavior so that an advisory
could be filed for the legacy crates. A maintainer replied on 2026-08-26 and
closed the issue as not planned: the `legacy` branch is unsupported, there are
no plans to update it, and users should move to crates built on `azure_core`
1.0.0 or newer.

[pr]: https://github.com/Azure/azure-sdk-for-rust/pull/1699
[issue]: https://github.com/Azure/azure-sdk-for-rust/issues/5074