CVE-2026-5559: PyBlade Remote Code Execution Vulnerability

LOW
Advisory Identifier: GHSA-23jg-5f8m-gw8c
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CVSS 6.3
CWE-791
Published
Advisory Summary

CVE-2026-5559 is a LOW (CVSS 6.3) remote code execution vulnerability (CWE-791: Incomplete Filtering of Special Elements) affecting PyBlade libraries in the PyPI ecosystem. The issue involves ssti/rce via bypassed ast validation in sandbox.py. Remediation is available in the latest vendor maintenance releases.

CVE-2026-5559 at a Glance

CVE Identifier CVE-2026-5559
GHSA Identifier GHSA-23jg-5f8m-gw8c
Severity LOW
CVSS v3.1 Base Score 6.3
CWE Classification CWE-791: Incomplete Filtering of Special Elements
Affected Product PyBlade
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 6.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability Low (A:L)

How to Fix CVE-2026-5559

To remediate this vulnerability, upgrade all affected PyBlade dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

pyblade fixed: Latest secure release 
pip install pyblade>=Latest secure release
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show pyblade

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-5559, inspect your installed packages using pip:

pip show pyblade

Analyze the terminal output to locate any version of PyBlade in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The pip show pyblade command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-791: Incomplete Filtering of Special Elements, where the product receives data from an upstream component, but does not completely filter special elements before sending it to a downstream component. In PyBlade, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

A vulnerability has been found in AntaresMugisho PyBlade 0.1.8-alpha/0.1.9-alpha. The affected element is the function _is_safe_ast of the file sandbox.py of the component AST Validation. Such manipulation leads to improper neutralization of special elements used in a template engine. The attack may be performed from remote. The exploit has been disclosed to the public and may be used. The project was informed of the problem early through an issue report but has not responded yet.

CVE-2026-5559 Affected PyBlade Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
pyblade
pypi/pyblade
PyPI
≥ 0.1.8-alpha
≤ 0.2.0-alpha

References

NVD — CVE-2026-5559 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-5559
PyBlade Source Repository REPOSITORY
https://github.com/AntaresMugisho/PyBlade/issues/1
PyBlade Source Repository REPOSITORY
https://github.com/AntaresMugisho/PyBlade/issues/1#issue-4086730906
PyBlade Source Repository REPOSITORY
https://github.com/AntaresMugisho/PyBlade
vuldb.com/submit/782904 WEB
https://vuldb.com/submit/782904
vuldb.com/vuln/355329 WEB
https://vuldb.com/vuln/355329
vuldb.com/vuln/355329/cti WEB
https://vuldb.com/vuln/355329/cti

Frequently Asked Questions

What is CVE-2026-5559?
CVE-2026-5559 is a security vulnerability in PyBlade involving SSTI/RCE via Bypassed AST Validation in sandbox.py under CWE-791: Incomplete Filtering of Special Elements.
Which PyBlade versions are affected?
Affected versions include releases prior to current release patches across affected packages: pyblade.
What version fixes CVE-2026-5559?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is pyblade affected?
Yes, pyblade is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of CVE-2026-5559?
CVE-2026-5559 has a CVSS v3.1 base score of 6.3 (LOW) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L.
What CWE is associated with CVE-2026-5559?
CVE-2026-5559 is classified under CWE-791: Incomplete Filtering of Special Elements (The product receives data from an upstream component, but does not completely filter special elements before sending it to a downstream component.).
How can I check PyPI dependencies for CVE-2026-5559?
Run the dependency tree command: 'pip show pyblade'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-23jg-5f8m-gw8c",
  "modified" : "2026-04-08T00:06:47Z",
  "published" : "2026-04-05T12:30:25Z",
  "aliases" : [ "CVE-2026-5559" ],
  "summary" : "PyBlade: SSTI/RCE via Bypassed AST Validation in sandbox.py",
  "details" : "A vulnerability has been found in AntaresMugisho PyBlade 0.1.8-alpha/0.1.9-alpha. The affected element is the function _is_safe_ast of the file sandbox.py of the component AST Validation. Such manipulation leads to improper neutralization of special elements used in a template engine. The attack may be performed from remote. The exploit has been disclosed to the public and may be used. The project was informed of the problem early through an issue report but has not responded yet.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "pyblade"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.1.8-alpha"
      }, {
        "last_affected" : "0.2.0-alpha"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-5559"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/AntaresMugisho/PyBlade/issues/1"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/AntaresMugisho/PyBlade/issues/1#issue-4086730906"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/AntaresMugisho/PyBlade"
  }, {
    "type" : "WEB",
    "url" : "https://vuldb.com/submit/782904"
  }, {
    "type" : "WEB",
    "url" : "https://vuldb.com/vuln/355329"
  }, {
    "type" : "WEB",
    "url" : "https://vuldb.com/vuln/355329/cti"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-791" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-08T00:06:47Z",
    "nvd_published_at" : "2026-04-05T11:16:55Z"
  }
}