Resource exhaustion in Pyasn1
CVE-2026-59885
pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.4, the BER, CER, and DER decoders process OBJECT IDENTIFIER and RELATIVE-OID values in quadratic time relative to the number of arcs, so a small crafted payload containing an OID with many arcs consumes excessive CPU per decode() call and can deny service to applications that decode untrusted ASN.1 data. The corresponding encoders have the same quadratic behavior when an application re-encodes previously decoded attacker-supplied values. This issue is fixed in version 0.6.4.
Vulnerability class: DoS (Denial of Service)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.006 (48.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 49th percentile — 48.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000
Affected products
- Pyasn1 — versions < 0.6.4
Weakness classification (CWE)
References
- github.com/pyasn1/pyasn1/commit/45bdb19eb7df4b3780fe9c912c63e99bffc39dd9 (Patch)
- github.com/pyasn1/pyasn1/releases/tag/v0.6.4 (Release Notes)
- github.com/pyasn1/pyasn1/security/advisories/GHSA-8ppf-4f7h-5ppj (Third Party Advisory)
Frequently asked questions
- What is CVE-2026-59885?
- CVE-2026-59885 is a high-severity vulnerability in Pyasn1, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-07-14.
- How severe is CVE-2026-59885?
- High severity. CVSS v3 base score is 7.5 out of 10.