# CVE-2026-119197: pyasn1 quadratic binary REAL mantissa decoding DoS

Source: https://junglewise.ai/threats/cve-2026-119197-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-2026-119197 · Severity: high · CVSS 7.5 · Published 2026-10-29

pyasn1 is a Python library that decodes ASN.1 data structures used in cryptography and network protocols. An attacker can craft malicious ASN.1 messages with specially crafted binary REAL numbers that cause the decoder to consume excessive CPU time, holding a single processor core for seconds or longer and potentially causing service outages.

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-2026-119197 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-119197 being exploited in the wild.

**How severe is CVE-2026-119197?** 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-2026-119197?** 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-2026-119197 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-119197?** 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 RealPayloadDecoder in pyasn1 prior to 0.6.5 processes binary REAL mantissas with quadratic time complexity, repeatedly performing left shift, bitwise OR, and byte string operations for each mantissa octet. An attacker can include a binary-encoded REAL with a large mantissa in ASN.1 data sent to a BER, CER, or DER decoder to trigger denial of service. The vulnerability requires network access to send crafted ASN.1 data and is not user-initiated.

## Affected products

- pyasn1 pyasn1 before 0.6.5

## Identifiers

- CVE-2026-119197
- GHSA-mm57-4v3p-rchx

## Timeline

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

## References

- [https://github.com/pyasn1/pyasn1/commit/ce3ec3390784780a530047e0e77be5ff457636a4](https://github.com/pyasn1/pyasn1/commit/ce3ec3390784780a530047e0e77be5ff457636a4)
- [https://github.com/pyasn1/pyasn1/pull/132](https://github.com/pyasn1/pyasn1/pull/132)

## Related threats

- [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 algorithm denial of service in ASN.1 decoding](https://junglewise.ai/threats/cve-2026-119195-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)