CVE-2026-59884
pyasn1 BER/CER/DER decoder denial of service via unbounded long-form tag IDs
CVSS Score
7.5
EPSS Score
0.0%
EPSS Percentile
0th
pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.4, the BER decoder shared by the CER and DER codecs parses long-form tags by accumulating continuation octets without an upper bound on the tag ID size, allowing a crafted input to force construction of an arbitrarily large integer with CPU cost growing quadratically and to trigger unhandled ValueError exceptions in Python 3.11+ error formatting paths. Any application decoding untrusted BER, CER, or DER input is affected. This issue is fixed in version 0.6.4.
| CWE | CWE-400 |
| Vendor | pyasn1 |
| Product | pyasn1 |
| Published | Jul 14, 2026 |
| Last Updated | Jul 15, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Affected Versions
pyasn1 / pyasn1
< 0.6.4