VulnerabilityAnalyzed

CVE-2026-59886

pyasn1 is a generic ASN.1 library for Python.

HIGH 7.5EPSS 0.34%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.34%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

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: 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS: 0.34% probability · 27th percentile
CISA KEV: Not listed
Weakness: CWE-400, CWE-770
Affected: pyasn1/pyasn1
Source: security-advisories@github.com

References

https://github.com/pyasn1/pyasn1/commit/e60c691cb91addb8fcefa2f537e85ede6fb1e886Patch
https://github.com/pyasn1/pyasn1/releases/tag/v0.6.4Release Notes
https://github.com/pyasn1/pyasn1/security/advisories/GHSA-hm4w-wwcw-mr6rThird Party Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.