Bug 2519409 (CVE-2026-75589)

Summary: CVE-2026-75589 perl-Net-OAuth: Net::OAuth: Information disclosure via timing attack in signature verification
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in Net::OAuth. This vulnerability arises from a non-constant-time comparison used when verifying HMAC-SHA1, HMAC-SHA256, and PLAINTEXT signatures. A remote attacker could exploit this by timing the responses to submitted messages, allowing them to recover valid signatures or, in the case of PLAINTEXT, sensitive consumer and token secrets one byte at a time. This leads to information disclosure, potentially compromising the integrity of communications.
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Bug Depends On: 2519561, 2519562    
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Description OSIDB Bzimport 2026-08-19 07:31:27 UTC 
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.