Bug 2452539 (CVE-2026-33936)

Summary: CVE-2026-33936 python-ecdsa: ecdsa: Denial of Service via crafted DER input
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: anthomas, dranck, dschmidt, ehelms, erezende, ggainey, jlanda, juwatts, kshier, lbrazdil, mhulan, mminar, nmoumoul, osousa, pcreech, rbiba, rchan, simaishi, smallamp, smcdonal, sskracic, stcannon, teagle, tmalecek, tpfromme, yguenane
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the `ecdsa` Python package, which is used for cryptographic operations. A remote attacker can exploit this vulnerability by sending a specially crafted data input, known as Distinguished Encoding Rules (DER). This malformed input can cause applications that process untrusted cryptographic keys to crash, leading to a denial of service.
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Description OSIDB Bzimport 2026-03-27 23:02:44 UTC 
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.