Vulnerability · Published Aug 19, 2026 · Assigned by CPANSec
CVE-2026-72889Net::OAuth versions before 0.33 for Perl allow the sender to choose the signature algorithm in verify
Critical 9.8
In plain English
A critical-severity security flaw in Net-OAuth. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 39% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | libnet-oauth-perl | no fix listed | DEBIAN-CVE-2026-72889 |
| Debian:13 | libnet-oauth-perl | no fix listed | DEBIAN-CVE-2026-72889 |
| Debian:14 | libnet-oauth-perl | 0.33-1 | DEBIAN-CVE-2026-72889 |
| Ubuntu:22.04:LTS | libnet-oauth-perl | no fix listed | UBUNTU-CVE-2026-72889 |
| Ubuntu:24.04:LTS | libnet-oauth-perl | no fix listed | UBUNTU-CVE-2026-72889 |
| Ubuntu:26.04:LTS | libnet-oauth-perl | no fix listed | UBUNTU-CVE-2026-72889 |
| Ubuntu:26.10 | libnet-oauth-perl | no fix listed | UBUNTU-CVE-2026-72889 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Net-OAuth | 0 – before 0.33 |
Weakness: CWE-347, CWE-757 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
References
- https://github.com/vurtdev/Net-OAuth/security/advisories/GHSA-c8rm-g5cm-4pf5 vendor-advisory
- https://github.com/vurtdev/Net-OAuth/commit/c467adf45c8d77ac4b92ad78b3eebf949252ba7f.patch patch
- https://metacpan.org/release/RRWO/Net-OAuth-0.33/changes release-notes
- https://datatracker.ietf.org/doc/html/rfc5849#section-3.4.2 technical-description
- https://datatracker.ietf.org/doc/html/rfc5849#section-3.4.3 technical-description
- http://www.openwall.com/lists/oss-security/2026/08/19/2