CVE-2026-119196
pyasn1: Quadratic CPU consumption in constructed BIT STRING decoding
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.
INFO
Published Date :
Oct. 29, 2026, 8:17 p.m.
Last Modified :
Nov. 4, 2026, 2:17 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | MITRE-CVE | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update pyasn1 library to version 0.6.5.
- Use a later version if available.
- Avoid processing untrusted BER/CER input.
- Validate input data structure and size.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-119196.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-119196 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-119196
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-119196 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-119196 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Nov. 04, 2026
Action Type Old Value New Value Added Reference https://github.com/pyasn1/pyasn1/security/advisories/GHSA-2qm8-x737-gmw5 Added SSVC {'id': 'CVE-2026-119196', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-11-04T01:40:25.017112Z'} -
New CVE Received by [email protected]
Oct. 29, 2026
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-407 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/119xxx/CVE-2026-119196.json">CVE-2026-119196</a> Added Reference https://github.com/pyasn1/pyasn1/commit/73ba7b043cc7e92cb37f16f2c955bff93b0e6f6c Added Reference https://github.com/pyasn1/pyasn1/pull/132 Added Reference https://github.com/pyasn1/pyasn1/releases/tag/v0.6.5 Added Reference https://github.com/pyasn1/pyasn1/security/advisories/GHSA-2qm8-x737-gmw5