# CVE-2026-72889: libnet-oauth-perl: Net::OAuth versions before 0.33 for Perl allow the sender to choose the signature algorithm in verify

CVE-2026-72889 is fixed in libnet-oauth-perl on 1 platform by DEBIAN-CVE-2026-72889 (version 0.33-1), released August 29, 2026. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2026-72889
- Priority: Urgent
- CVSS: 9.8 (critical)
- EPSS: 0.0045
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 19, 2026

## Description

Net::OAuth versions before 0.33 for Perl allow the sender to choose the signature algorithm in verify.  verify resolves the signature method class from the signature_method parameter of the incoming message. signature_method is required on every request, so the algorithm used to check a signature is chosen by whoever sent it, and nothing lets the verifying party pin the method instead. When a message names HMAC-SHA1 or HMAC-SHA256, the key is derived from consumer_secret and token_secret rather than from the key the provider deployed.  A provider deployed on RSA-SHA1 holds only the consumer public key, and RFC 5849 does not use consumer_secret for that method, so the required parameter is filled with a placeholder. A client that names HMAC-SHA1 instead has its signature checked against that placeholder, so a guessable one is enough to forge requests for any consumer key and token.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libnet-oauth-perl Debian 14 | 0.33-1 | [DEBIAN-CVE-2026-72889](https://patchblox.com/security/data/fix/linux/debian-cve-2026-72889.md) | Aug 29, 2026 |

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Data as of 2026-11-10T01:44:33Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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