# CVE-2026-75589: libnet-oauth-perl: Net::OAuth versions before 0.33 for Perl check HMAC-SHA1, HMAC-SHA256 and PLAINTEXT signatures with a non-constant-ti...

CVE-2026-75589 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-75589, released August 29, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-75589
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0051
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Aug 19, 2026

## Description

Net::OAuth versions before 0.33 for Perl check HMAC-SHA1, HMAC-SHA256 and PLAINTEXT signatures with a non-constant-time comparison in verify.  Each of the three compares the signature carried in the message against the locally computed one with the eq operator, which returns as soon as the two strings differ. The time taken to reject a signature varies with the length of the matching prefix. RSA-SHA1 is not affected, as it verifies through the RSA key object rather than by comparing strings.  A client that can submit messages and time the replies may recover a valid signature one byte at a time rather than searching the whole signature space. Under PLAINTEXT the value compared against is the signature key itself, so the search recovers consumer_secret and token_secret.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libnet-oauth-perl Debian 14 | 0.33-1 | [DEBIAN-CVE-2026-75589](https://patchblox.com/security/data/fix/linux/debian-cve-2026-75589.md) | Aug 29, 2026 |
| Linux | perl-Net-OAuth Fedora 43 | 0.33-1.fc43 | [FEDORA-2026-370BD8B5F0](https://patchblox.com/security/data/fix/linux/fedora-2026-370bd8b5f0.md) | Aug 30, 2026 |

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Data as of 2026-11-08T19:12:23Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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