CVE-2026-59884
High
Description
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.
SeverityHigh
CVSS7.5
Exploit probability—
ProductPyasn1
PublishedJul 14, 2026
First seenJul 14, 2026
Weakness typeCWE-400Uncontrolled resource consumption
How to fix
Update
- pyasn1 pyasn10.6.4 or later
- pyasn10.6.4 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| pyasn1 pyasn1 | v < 0.6.4 | 0.6.4 |
| pyasn1PyPI | v < 0.6.4 | 0.6.4 |
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