high7.5
CVE-2026-119196
pyasn1 has quadratic CPU consumption in constructed BIT STRING decoding
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | pyasn1 | <= 0.6.4 | 0.6.5 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Pyasn1 | Pyasn1 | before 0.6.5 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-2qm8-x737-gmw5
- https://github.com/pyasn1/pyasn1/security/advisories/GHSA-2qm8-x737-gmw5
- https://nvd.nist.gov/vuln/detail/CVE-2026-119196
- https://github.com/pyasn1/pyasn1/pull/132
- https://github.com/pyasn1/pyasn1/commit/73ba7b043cc7e92cb37f16f2c955bff93b0e6f6c
- https://github.com/pyasn1/pyasn1/releases/tag/v0.6.5