CVE-2026-119196 pyasn1: Quadratic CPU consumption in constructed BIT STRING decoding
- Exploited in the wild
- Not known
- Fix
- None listed
What is CVE-2026-119196?
CVE-2026-119196 is a high-severity vulnerability in pyasn1, published on 29 Oct 2026.
Official description
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.
Weakness: CWE-407
Which versions are affected by CVE-2026-119196?
How do I fix CVE-2026-119196?
No fix has been published for CVE-2026-119196 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-119196 being exploited?
There is no known exploitation of CVE-2026-119196 in the wild and no public exploit code.