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Vulnerability record · CVE-2026-59884 · published 14 July 2026

CVE-2026-59884: Pyasn1 uncontrolled resource consumption vulnerability

PPyasn1 · Pyasn1

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.

7.5 CVSS 3.1 High EPSS 0.62% · top 52.6% CWE-400 · Uncontrolled resource consumption
7.5CVSS 3.1 base score
0.62%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References
21 Jul 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/pyasn1/pyasn1/commit/628e36ecbb5277a3f01572ce418ef54271b165a5 Patch
https://github.com/pyasn1/pyasn1/releases/tag/v0.6.4 Release Notes
https://github.com/pyasn1/pyasn1/security/advisories/GHSA-m4p7-r5rc-7g4j Third Party Advisory

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-59884), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.