GHSA-2qm8-x737-gmw5: pyasn1 (CVE-2026-119196)

Package	Ecosystem	Affected	Fixed in
pyasn1	PyPI	<0.6.5	0.6.5

Machine-written summary

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

Affected: pyasn1 versions below 0.6.5 (through 0.6.4), where decoding a constructed BIT STRING with many fragments takes CPU time that grows quadratically with input size. An attacker who can supply large ASN.1 data to an application that decodes it with the BER or CER decoder, or with the DER decoder when given a matching schema, can cause CPU exhaustion during decoding, leading to denial of service. Upgrade to pyasn1 0.6.5, which fixes the issue; until then, limit the size of untrusted ASN.1 input before decoding, or reject constructed BIT STRING encodings where the protocol permits.

Written 31 Oct 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 0.0043, the 36th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

29 Oct 2026, 19:44 UTC Confirmed by the CVE List
29 Oct 2026, 20:17 UTC Confirmed by NVD
31 Oct 2026, 14:07 UTC First seen by agentprime
31 Oct 2026, 14:07 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.