CVE-2026-24408: Sigstore Sigstore CSRF Possibility Vulnerability

LOW
Advisory Identifier: GHSA-hm8f-75xx-w2vr
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CVSS 0.0
CWE-352
Published
Advisory Summary

CVE-2026-24408 is a LOW (CVSS 0.0) sigstore csrf possibility vulnerability (CWE-352: Cross-Site Request Forgery (CSRF)) affecting Sigstore libraries in the PyPI ecosystem. The issue involves sigstore csrf possibility in oidc authentication during signing. Remediation is available by upgrading affected packages to version 4.2.0.

CVE-2026-24408 at a Glance

CVE Identifier CVE-2026-24408
GHSA Identifier GHSA-hm8f-75xx-w2vr
Severity LOW
CVSS v3.1 Base Score 0.0
CWE Classification CWE-352: Cross-Site Request Forgery (CSRF)
Affected Product Sigstore
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 0.0

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

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

How to Fix CVE-2026-24408

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

sigstore fixed: 4.2.0 
pip install sigstore>=4.2.0
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 sigstore

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-24408, inspect your installed packages using pip:

pip show sigstore

Analyze the terminal output to locate any version of Sigstore in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.2.0), your application is affected.

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

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-352: Cross-Site Request Forgery (CSRF), where the web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor. In Sigstore, 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

### Summary The sigstore-python OAuth authentication flow is susceptible to Cross-Site Request Forgery. ### Details `_OAuthSession` creates a unique "state" and sends it as a parameter in the authentication request but the "state" in the server response seems not not be cross-checked with this value. Fix should be fairly trivial. ### Impact This should be low impact: A man-in-the middle attacker could trick a sigstore-python user into signing something with an identity controlled by the attacker (by returning the response to an authentication request they created). This would be quite confusing but not dangerous.

CVE-2026-24408 Affected Sigstore Versions

1 component(s)
Fixed Versions:
4.2.0
Product / Package Ecosystem Affected Versions Fixed Version
sigstore
pypi/sigstore
PyPI
< 4.2.0
4.2.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/sigstore/sigstore-python/security/advisories/GHSA-hm8f-75xx-w2vr
NVD — CVE-2026-24408 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-24408
Security Fix Commit FIX COMMIT
https://github.com/sigstore/sigstore-python/commit/5e77497fe8f0b202bdd118949074ec2f20da69aa
Sigstore Source Repository REPOSITORY
https://github.com/sigstore/sigstore-python
Sigstore Release RELEASE
https://github.com/sigstore/sigstore-python/releases/tag/v4.2.0

Frequently Asked Questions

What is CVE-2026-24408?
CVE-2026-24408 is a security vulnerability in Sigstore involving sigstore CSRF possibility in OIDC authentication during signing under CWE-352: Cross-Site Request Forgery (CSRF).
Which Sigstore versions are affected?
Affected versions include releases prior to 4.2.0 across affected packages: sigstore.
What version fixes CVE-2026-24408?
Upgrading to 4.2.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is sigstore affected?
Yes, sigstore is affected in releases prior to 4.2.0. Upgrade your dependency to 4.2.0 or later.
What is the CVSS score of CVE-2026-24408?
CVE-2026-24408 has a CVSS v3.1 base score of 0.0 (LOW) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:N.
What CWE is associated with CVE-2026-24408?
CVE-2026-24408 is classified under CWE-352: Cross-Site Request Forgery (CSRF) (The web application does not, or cannot, sufficiently verify whether a request was intentionally provided by the user who sent the request, which could have originated from an unauthorized actor.).
How can I check PyPI dependencies for CVE-2026-24408?
Run the dependency tree command: 'pip show sigstore'. 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-hm8f-75xx-w2vr",
  "modified" : "2026-01-29T03:24:33Z",
  "published" : "2026-01-26T21:34:50Z",
  "aliases" : [ "CVE-2026-24408" ],
  "summary" : "sigstore CSRF possibility in OIDC authentication during signing",
  "details" : "### Summary\n\nThe sigstore-python OAuth authentication flow is susceptible to Cross-Site Request Forgery.\n\n### Details\n\n`_OAuthSession` creates a unique \"state\" and sends it as a parameter in the authentication request but the \"state\" in the server response seems not not be cross-checked with this value. \n\nFix should be fairly trivial.\n\n### Impact\n\nThis should be low impact: A man-in-the middle attacker could trick a sigstore-python user into signing something with an identity controlled by the attacker (by returning the response to an authentication request they created). This would be quite confusing but not dangerous.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "sigstore"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.2.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/sigstore/sigstore-python/security/advisories/GHSA-hm8f-75xx-w2vr"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-24408"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sigstore/sigstore-python/commit/5e77497fe8f0b202bdd118949074ec2f20da69aa"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/sigstore/sigstore-python"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sigstore/sigstore-python/releases/tag/v4.2.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-352" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-01-26T21:34:50Z",
    "nvd_published_at" : "2026-01-26T23:16:08Z"
  }
}