GHSA-hm4w-wwcw-mr6r: pyasn1 (CVE-2026-59886)

Package	Ecosystem	Affected	Fixed in
pyasn1	PyPI	<0.6.4	0.6.4

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

Affected are pyasn1 versions before 0.6.4, where converting a decoded REAL value to a float can take excessive CPU and memory, hanging the process. An attacker only needs to supply a short encoded REAL value with a very large exponent to untrusted decoders, and the hang occurs when the decoded value is printed, compared, or converted to float; decoding alone does not trigger it. Upgrade to pyasn1 0.6.4 or later, which fixes the issue.

Written 5 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
7.5	High	3.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	CNA (GitHub_M)

CISA KEV Not listed.
EPSS 0.0044, the 38th percentile, on 15 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 14:35 UTC First seen by agentprime
31 Oct 2026, 14:35 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.