High severity · published Jul 14, 2026
CVE-2026-59886
pyasn1: Uncontrolled resource consumption when converting decoded REAL values
7.5
CVSS
0.6%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 49% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
PY
pyasn1 · pyasn1
< 0.6.4 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-59886
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-59886
Patch
https://github.com/pyasn1/pyasn1/commit/e60c691cb91addb8fcefa2f537e85ede6fb1e886
Release Notes
https://github.com/pyasn1/pyasn1/releases/tag/v0.6.4
Third Party Advisory
https://github.com/pyasn1/pyasn1/security/advisories/GHSA-hm4w-wwcw-mr6r
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pyasn1 is a generic ASN.1 library for Python