Vulnerability in Pyasn1
CVE-2026-119196
pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.5, constructed BIT STRING decoding repeatedly shifts and copies the complete bit value accumulated from earlier fragments. Attacker-controlled BER or CER input contains many constructed BIT STRING fragments; schema-driven DER also accepts a definite-length constructed BIT STRING. BitStringPayloadDecoder repeatedly calls BitString.fromOctetString with the prior bitString as prepend, shifting an ever-growing SizedInteger for each fragment and causing quadratic work. Large fragmented values can exhaust CPU during decode() without requiring later conversion or formatting. This issue is fixed in version 0.6.5.
Published .
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
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Pyasn1 — versions < 0.6.5
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-119196?
- CVE-2026-119196 is a high-severity vulnerability in Pyasn1, classified under Inefficient Algorithmic Complexity. CVSS score: 7.5/10. Published 2026-10-29.
- How severe is CVE-2026-119196?
- High severity. CVSS v3 base score is 7.5 out of 10.