# CVE-2026-75589: Net::OAuth versions before 0.33 for Perl check HMAC-SHA1, HMAC-SHA256 and PLAINTEXT signatures with a non-constant-time comparison in verify.

> Timing side-channel in Net::OAuth allows attackers to recover valid signatures and secrets via non-constant-time comparison.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Aug 2026
- **Updated:** 26 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-75589, GHSA-g8xr-69p3-gw56, UBUNTU-CVE-2026-75589

## What is CVE-2026-75589?

CVE-2026-75589 is a high-severity vulnerability, published on 19 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-208 (Observable Timing Discrepancy)

## Which versions are affected by CVE-2026-75589?


## How do I fix CVE-2026-75589?

Upgrade to a fixed version.

## Is CVE-2026-75589 being exploited?

There is no known exploitation of CVE-2026-75589 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-75589 and fix it if it is affected.

What it is: CVE-2026-75589 is a high-severity vulnerability, published on 19 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-75589 in the wild and no public exploit code.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-75589/ (Markdown: https://insights.sbomify.com/CVE-2026-75589/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-75589
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-75589
- OSV: https://osv.dev/vulnerability/CVE-2026-75589

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-75589/
Summaries are generated and may contain mistakes; the official description above is the record.