high7.5
CVE-2026-119194
pyasn1 has quadratic CPU use in schemaless BER/CER/DER container decoding
Impact
pyasn1 is a generic ASN.1 library for Python. From 0.3.3 until 0.6.5, schemaless container decoding stores every decoded component's TagSet in a growing set even though only one-versus-multiple tag types must be distinguished. Attacker-controlled BER, CER, or DER input contains many distinct long tag IDs whose TagSet hashes collide. Each later set insertion compares against an increasing number of earlier colliding tags in ConstructedPayloadDecoderBase._decodeComponentsSchemaless, producing quadratic CPU work while decoded values and order remain valid. Repeated inputs can exhaust decoder CPU and reduce service availability. This issue is fixed in version 0.6.5.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | pyasn1 | >= 0.3.3, < 0.6.5 | 0.6.5 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Pyasn1 | Pyasn1 | from 0.3.3, before 0.6.5 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-fm9c-5rcf-2q5p
- https://github.com/pyasn1/pyasn1/security/advisories/GHSA-fm9c-5rcf-2q5p
- https://nvd.nist.gov/vuln/detail/CVE-2026-119194
- https://github.com/pyasn1/pyasn1/pull/132
- https://github.com/pyasn1/pyasn1/commit/a36e3a3d067148d26197a6b7221fd0e2cde9cc86
- https://github.com/pyasn1/pyasn1/releases/tag/v0.6.5