{"id":"CVE-2026-33936","state":"PUBLISHED","title":"python-ecdsa: Denial of Service via improper DER length validation in crafted private keys","description":"The `ecdsa` PyPI package is a pure Python implementation of ECC (Elliptic Curve Cryptography) with support for ECDSA (Elliptic Curve Digital Signature Algorithm), EdDSA (Edwards-curve Digital Signature Algorithm) and ECDH (Elliptic Curve Diffie-Hellman). Prior to version 0.19.2, an issue in the low-level DER parsing functions can cause unexpected exceptions to be raised from the public API functions. `ecdsa.der.remove_octet_string()` accepts truncated DER where the encoded length exceeds the available buffer. For example, an OCTET STRING that declares a length of 4096 bytes but provides only 3 bytes is parsed successfully instead of being rejected. Because of that, a crafted DER input can cause `SigningKey.from_der()` to raise an internal exception (`IndexError: index out of bounds on dimension 1`) rather than cleanly rejecting malformed DER (e.g., raising `UnexpectedDER` or `ValueError`). Applications that parse untrusted DER private keys may crash if they do not handle unexpected exceptions, resulting in a denial of service. Version 0.19.2 patches the issue.","publishedAt":"2026-03-27T22:08:22.868Z","updatedAt":"2026-04-01T13:44:46.297Z","severity":{"score":5.3,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","source":"GitHub_M"},"assigner":"GitHub_M","products":["tlsfuzzer python-ecdsa"],"affected":[{"vendor":"tlsfuzzer","product":"python-ecdsa","versions":[{"version":"< 0.19.2","status":"affected"}]}],"references":["https://github.com/tlsfuzzer/python-ecdsa/security/advisories/GHSA-9f5j-8jwj-x28g","https://github.com/tlsfuzzer/python-ecdsa/commit/bd66899550d7185939bf27b75713a2ac9325a9d3","https://github.com/tlsfuzzer/python-ecdsa/releases/tag/python-ecdsa-0.19.2"],"weaknesses":["CWE-20","CWE-130"],"ingestedAt":"2026-10-29T20:11:40.391Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/33xxx/CVE-2026-33936.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-33936","state":"PUBLISHED","datePublished":"2026-03-27T22:08:22.868Z","dateUpdated":"2026-04-01T13:44:46.297Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-03-24T19:50:52.103Z"},"containers":{"cna":{"title":"python-ecdsa: Denial of Service via improper DER length validation in crafted private keys","descriptions":[{"lang":"en","value":"The `ecdsa` PyPI package is a pure Python implementation of ECC (Elliptic Curve Cryptography) with support for ECDSA (Elliptic Curve Digital Signature Algorithm), EdDSA (Edwards-curve Digital Signature Algorithm) and ECDH (Elliptic Curve Diffie-Hellman). Prior to version 0.19.2, an issue in the low-level DER parsing functions can cause unexpected exceptions to be raised from the public API functions. `ecdsa.der.remove_octet_string()` accepts truncated DER where the encoded length exceeds the available buffer. For example, an OCTET STRING that declares a length of 4096 bytes but provides only 3 bytes is parsed successfully instead of being rejected. Because of that, a crafted DER input can cause `SigningKey.from_der()` to raise an internal exception (`IndexError: index out of bounds on dimension 1`) rather than cleanly rejecting malformed DER (e.g., raising `UnexpectedDER` or `ValueError`). Applications that parse untrusted DER private keys may crash if they do not handle unexpected exceptions, resulting in a denial of service. Version 0.19.2 patches the issue."}],"affected":[{"vendor":"tlsfuzzer","product":"python-ecdsa","versions":[{"version":"< 0.19.2","status":"affected"}]}],"references":[{"url":"https://github.com/tlsfuzzer/python-ecdsa/security/advisories/GHSA-9f5j-8jwj-x28g","name":"https://github.com/tlsfuzzer/python-ecdsa/security/advisories/GHSA-9f5j-8jwj-x28g","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/tlsfuzzer/python-ecdsa/commit/bd66899550d7185939bf27b75713a2ac9325a9d3","name":"https://github.com/tlsfuzzer/python-ecdsa/commit/bd66899550d7185939bf27b75713a2ac9325a9d3","tags":["x_refsource_MISC"]},{"url":"https://github.com/tlsfuzzer/python-ecdsa/releases/tag/python-ecdsa-0.19.2","name":"https://github.com/tlsfuzzer/python-ecdsa/releases/tag/python-ecdsa-0.19.2","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"LOW","baseScore":5.3,"baseSeverity":"MEDIUM","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-20","lang":"en","description":"CWE-20: Improper Input Validation","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-130","lang":"en","description":"CWE-130: Improper Handling of Length Parameter Inconsistency","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-03-27T22:08:22.868Z"},"source":{"advisory":"GHSA-9f5j-8jwj-x28g","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-04-01T13:44:27.418372Z","id":"CVE-2026-33936","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-04-01T13:44:46.297Z"}}]}}}