Vulnerability Details CVE-2026-33936
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.0
EPSS Ranking 14.4%
CVSS Severity
CVSS v3 Score 5.3
Products affected by CVE-2026-33936
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cpe:2.3:a:tlsfuzzer:ecdsa:0.10
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cpe:2.3:a:tlsfuzzer:ecdsa:0.11
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cpe:2.3:a:tlsfuzzer:ecdsa:0.12
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cpe:2.3:a:tlsfuzzer:ecdsa:0.13
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cpe:2.3:a:tlsfuzzer:ecdsa:0.13.1
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cpe:2.3:a:tlsfuzzer:ecdsa:0.13.2
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cpe:2.3:a:tlsfuzzer:ecdsa:0.13.3
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cpe:2.3:a:tlsfuzzer:ecdsa:0.14
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cpe:2.3:a:tlsfuzzer:ecdsa:0.14.1
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cpe:2.3:a:tlsfuzzer:ecdsa:0.15
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cpe:2.3:a:tlsfuzzer:ecdsa:0.16.0
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cpe:2.3:a:tlsfuzzer:ecdsa:0.16.1
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cpe:2.3:a:tlsfuzzer:ecdsa:0.17.0
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cpe:2.3:a:tlsfuzzer:ecdsa:0.5
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cpe:2.3:a:tlsfuzzer:ecdsa:0.6
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cpe:2.3:a:tlsfuzzer:ecdsa:0.7
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cpe:2.3:a:tlsfuzzer:ecdsa:0.8
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cpe:2.3:a:tlsfuzzer:ecdsa:0.9