Predictive Vulnerability Intelligence.

Product

  • Product
  • Pricing
  • Documentation

Company

  • About
  • Partnerships
  • Blog
  • Support

Legal

  • Terms
  • Privacy
  • Data Licensing

© 2026 FAUCET Technologies LLC. All rights reserved.

CVE-2026-59884

35
FAUCET Score

pyasn1 is a generic ASN.1 library for Python. Prior to 0.6.4, the BER decoder shared by the CER and DER codecs parses long-form tags by accumulating continuation octets without an upper bound on the tag ID size, allowing a crafted input to force construction of an arbitrarily large integer with CPU cost growing quadratically and to trigger unhandled ValueError exceptions in Python 3.11+ error formatting paths. Any application decoding untrusted BER, CER, or DER input is affected. This issue is fixed in version 0.6.4.

First published: Jul 14, 2026Last modified: Jul 14, 2026

Impacted Technologies

VendorProductVersion(s)CPE
< 0.6.4CPE matchmatch criteria
cpe:2.3:a:pyasn1:pyasn1:*:*:*:*:*:python:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.35%
Probability of exploitation in next 30 days
EPSS Percentile
27.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0035 is in the 8th percentile among its peer group of 51,551 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (3)

github_advisorypatch availablevia nvd_reference
View patch
microsoftpatch availablevia msrc
Product: azl3 python-pyasn1 0.4.8-2 on Azure Linux 3.0Fixed in: 0.4.8-3
pippatch availablevia ghsa
Product: pyssn1Fixed in: 0.6.4

Vendor Advisories (2)

pipGHSA-m4p7-r5rc-7g4jhigh

pyasn1 BER/CER/DER decoder denial of service via unbounded long-form tag IDs

Jul 21, 2026
microsoft2026-Jul/CVE-2026-59884Important

pyasn1 BER/CER/DER decoder denial of service via unbounded long-form tag IDs

Jul 14, 2026

References

github.com / pyasn1/pyasn1/commit/628e36ecbb5277a3f01572ce418ef54271b165a5
Patch
github.com / pyasn1/pyasn1/releases/tag/v0.6.4
Release Notes
github.com / pyasn1/pyasn1/security/advisories/GHSA-m4p7-r5rc-7g4j
Third Party Advisory