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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
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.
Sources
Also known as DEBIAN-CVE-2026-75589, GHSA-g8xr-69p3-gw56, UBUNTU-CVE-2026-75589.