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Vulnerability record · CVE-2026-59886 · published 14 July 2026

CVE-2026-59886: Pyasn1 uncontrolled resource consumption vulnerability

PPyasn1 · Pyasn1

pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.4, the univ.Real type converted its mantissa, base, and exponent value to a Python float using exact big-integer exponentiation. A BER, CER, or DER encoded REAL value only a few bytes long can carry a very large exponent, causing float conversion through prettyPrint(), str(), comparison, arithmetic, int(), or an explicit float() call to consume excessive CPU and memory and hang applications that decode untrusted ASN.1 data and then print, log, or compare decoded objects. 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 consumptionCWE-770 · Allocation without limits
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 univ.Real type converted its mantissa, base, and exponent value to a Python float using exact big-integer exponentiation. A BER, CER, or DER encoded REAL value only a few bytes long can carry a very large exponent, causing float conversion through prettyPrint(), str(), comparison, arithmetic, int(), or an explicit float() call to consume excessive CPU and memory and hang applications that decode untrusted ASN.1 data and then print, log, or compare decoded objects. 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/e60c691cb91addb8fcefa2f537e85ede6fb1e886 Patch
https://github.com/pyasn1/pyasn1/releases/tag/v0.6.4 Release Notes
https://github.com/pyasn1/pyasn1/security/advisories/GHSA-hm4w-wwcw-mr6r 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-2026-59886), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.