CVSS 3.1
7.5 highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HCVE-2026-59884
High (7.5) in pyasn1 pyasn1. EPSS 0.6% chance of exploitation in the next 30 days. Fixed in pyasn1 0.6.4.
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.
Severity
- EPSS
- 0.6% chance of exploitation in the next 30 days; higher than 49% of CVEs (scores of 2026-10-31)
- CWE
- CWE-400
- Published
- Modified
- Record from
- the NVD, synced
Affected
- pyasn1:pyasn1
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-m4p7-r5rc-7g4j | PyPI | pyasn1 | <0.6.4 | 0.6.4 |
| PYSEC-2026-3455 | PyPI | pyasn1 | <0.6.4 | 0.6.4 |