A flaw was found in all python-ecdsa versions before 0.13.3, where it did not correctly verify whether signatures used DER encoding. Without this verification, a malformed signature could be accepted, making the signature malleable. Without proper verification, an attacker could use a malleable signature to create false transactions.
{
"nvd_published_at": "2020-01-02T15:15:00Z",
"severity": "CRITICAL",
"github_reviewed": true,
"cwe_ids": [
"CWE-347"
],
"github_reviewed_at": "2020-04-01T15:40:54Z"
}