Vulnerability in Pyasn1
CVE-2026-119197
pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.5, binary REAL decoding builds a large mantissa one octet at a time by shifting a growing integer and slicing the remaining byte string. Attacker-controlled ASN.1 includes a binary-encoded REAL with a large mantissa and reaches BER, CER, or DER decode(), with or without a schema containing REAL. RealPayloadDecoder.valueDecoder repeatedly performs a left shift, OR, and suffix copy for every mantissa octet, making decode time quadratic in mantissa length. A comparatively small REAL value can hold a decoding worker on one CPU core for seconds or longer and cause availability loss. 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-2026-119197?
- CVE-2026-119197 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-2026-119197?
- High severity. CVSS v3 base score is 7.5 out of 10.