# CVE-2026-119195: pyasn1 quadratic algorithm denial of service in ASN.1 decoding

Source: https://junglewise.ai/threats/cve-2026-119195-pyasn1-is-a-generic-asn-1-library-for-python-prior-to-0-6-5  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-29. Updated: 2026-10-29  
License: CC BY 4.0 with a link back

CVE-2026-119195 · Severity: high · CVSS 7.5 · Published 2026-10-29

pyasn1 is a Python library for encoding and decoding ASN.1 data, which is used in security protocols and data interchange. An attacker can send specially crafted ASN.1 messages with many small fragments that trigger quadratic-time reassembly operations, consuming CPU resources and causing the application to slow down or become unresponsive. This attack requires no authentication or user interaction and cannot be used to steal or modify data.

Technologies: [Pyasn1](https://junglewise.ai/threats/technologies/pyasn1), [pyasn1 (PyPI)](https://junglewise.ai/threats/technologies/pypi-pyasn1). Vendors: [Pyasn1](https://junglewise.ai/threats/vendors/pyasn1), [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-119195 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-119195 being exploited in the wild.

**How severe is CVE-2026-119195?** High severity, with a CVSS score of 7.5, published 29 October 2026.

**Which products and versions are affected?** Pyasn1 before 0.6.5; pyasn1 (PyPI) <= 0.6.4, ECOSYSTEM:introduced=0,fixed=0.6.5.

**Is there a fix for CVE-2026-119195?** Yes. pyasn1 (PyPI): upgrade to 0.6.5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-119195 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-119195?** Check whether you run Pyasn1 or pyasn1 (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- pyasn1 (PyPI): upgrade to 0.6.5 or later

  ```sh
  pip install "pyasn1>=0.6.5"
  ```


## Technical details

The vulnerability exists in the BER/CER/DER decoder's handling of constructed OCTET STRINGs and indefinite-length ANY values. The OctetStringPayloadDecoder and AnyPayloadDecoder use algorithms that repeatedly concatenate fragments onto a growing bytes object, resulting in O(n²) complexity; an attacker controlling the BER/CER encoded input can trigger this by sending many small fragments. The issue is fixed by changing the reassembly strategy to avoid quadratic copying.

## Affected products

- pyasn1 pyasn1 before 0.6.5

## Identifiers

- CVE-2026-119195
- GHSA-9m75-vc3g-4x39

## Timeline

- 2026-10-29: disclosed
- 2026-10-27: patched

## References

- [https://github.com/pyasn1/pyasn1/commit/4ce00797c594b59c1fd6b86d9ebc3ba87b7ec9f9](https://github.com/pyasn1/pyasn1/commit/4ce00797c594b59c1fd6b86d9ebc3ba87b7ec9f9)
- [https://github.com/pyasn1/pyasn1/pull/132](https://github.com/pyasn1/pyasn1/pull/132)

## Related threats

- [pyasn1 quadratic binary REAL mantissa decoding DoS](https://junglewise.ai/threats/cve-2026-119197-pyasn1-is-a-generic-asn-1-library-for-python-prior-to-0-6-5)
- [pyasn1 quadratic CPU exhaustion in BIT STRING decoding](https://junglewise.ai/threats/cve-2026-119196-pyasn1-is-a-generic-asn-1-library-for-python-prior-to-0-6-5)
- [pyasn1 quadratic CPU use in schemaless container decoding](https://junglewise.ai/threats/cve-2026-119194-pyasn1-is-a-generic-asn-1-library-for-python-from-0-3-3-until-0)
- [pyasn1 resource consumption in univ.Real float conversion](https://junglewise.ai/threats/cve-2026-59886-pyasn1-resource-consumption-in-univ-real-float-conversion)
- [pyasn1 algorithmic complexity denial of service in OID processing](https://junglewise.ai/threats/cve-2026-59885-pyasn1-algorithmic-complexity-denial-of-service-in-oid-processing)