CVE-2026-76847: Software Security Vulnerability Vulnerability

HIGH
Advisory Identifier: GHSA-crfw-6q9f-w49f
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CVSS 8.8
CWE-321
Published
Advisory Summary

CVE-2026-76847 is a HIGH (CVSS 8.8) security vulnerability vulnerability (CWE-321: Use of Hard-coded Cryptographic Key) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product uses a hard-coded, unchangeable cryptographic key.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-76847 at a Glance

CVE Identifier CVE-2026-76847
GHSA Identifier GHSA-crfw-6q9f-w49f
Severity HIGH
CVSS v3.1 Base Score 8.8
CWE Classification CWE-321: Use of Hard-coded Cryptographic Key
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 8.8

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

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

How to Fix CVE-2026-76847

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

Verify Direct and Transitive Dependencies

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

mvn dependency:tree

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-76847, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree

Analyze the terminal output to locate any version of Software 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 mvn dependency:tree command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-321: Use of Hard-coded Cryptographic Key, where the product uses a hard-coded, unchangeable cryptographic key. In Software, 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

act starts an HTTP Artifacts V4 backend whenever a workflow uses actions/upload-artifact@v4 or actions/download-artifact@v4. The control-plane RPCs of that backend, including CreateArtifact, GetSignedArtifactURL, ListArtifacts, FinalizeArtifact and DeleteArtifact, accept a caller-supplied workflow_run_backend_id and never check that it belongs to the requester: validateRunIDV4 in pkg/artifacts/artifacts_v4.go parses the value and returns it with the comparison against the requesting task's run ID left commented out. The signed URLs the backend issues are authenticated by an HMAC whose key is hardcoded to the four bytes 0xba 0xdb 0xee 0xf0, identical in every build, computed over a concatenation of endpoint, expiry, artifact name and task ID with no length prefix or delimiter, so signatures are both forgeable and ambiguous between differing artifact name and task ID pairs. The --artifact-server-addr flag defaults to the host's outbound address rather than loopback, leaving the backend reachable from the surrounding network. Any client that can reach it may read, overwrite or delete the artifacts of a concurrently running job with no credentials, exposing build outputs such as secrets and deployment credentials and permitting their replacement before the owning job consumes them.

References

NVD — CVE-2026-76847 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-76847
Software Source Repository REPOSITORY
https://github.com/nektos/act
Software Source Repository REPOSITORY
https://github.com/nektos/act/blob/v0.2.89/cmd/root.go
Software Source Repository REPOSITORY
https://github.com/nektos/act/blob/v0.2.89/pkg/artifacts/artifacts_v4.go
www.vulncheck.com/advisories/act-thro... WEB
https://www.vulncheck.com/advisories/act-through-missing-authorization-in-the-artifacts-v4-backend

Frequently Asked Questions

What is CVE-2026-76847?
CVE-2026-76847 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-321: Use of Hard-coded Cryptographic Key.
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-76847?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-76847?
CVE-2026-76847 has a CVSS v3.1 base score of 8.8 (HIGH) with vector string CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-76847?
CVE-2026-76847 is classified under CWE-321: Use of Hard-coded Cryptographic Key (The product uses a hard-coded, unchangeable cryptographic key.).
How can I check Maven dependencies for CVE-2026-76847?
Run the dependency tree command: 'mvn dependency:tree'. 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 
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  "schema_version" : "1.4.0",
  "id" : "GHSA-crfw-6q9f-w49f",
  "modified" : "2026-08-24T15:31:51Z",
  "published" : "2026-08-24T15:31:51Z",
  "aliases" : [ "CVE-2026-76847" ],
  "details" : "act starts an HTTP Artifacts V4 backend whenever a workflow uses actions/upload-artifact@v4 or actions/download-artifact@v4. The control-plane RPCs of that backend, including CreateArtifact, GetSignedArtifactURL, ListArtifacts, FinalizeArtifact and DeleteArtifact, accept a caller-supplied workflow_run_backend_id and never check that it belongs to the requester: validateRunIDV4 in pkg/artifacts/artifacts_v4.go parses the value and returns it with the comparison against the requesting task's run ID left commented out. The signed URLs the backend issues are authenticated by an HMAC whose key is hardcoded to the four bytes 0xba 0xdb 0xee 0xf0, identical in every build, computed over a concatenation of endpoint, expiry, artifact name and task ID with no length prefix or delimiter, so signatures are both forgeable and ambiguous between differing artifact name and task ID pairs. The --artifact-server-addr flag defaults to the host's outbound address rather than loopback, leaving the backend reachable from the surrounding network. Any client that can reach it may read, overwrite or delete the artifacts of a concurrently running job with no credentials, exposing build outputs such as secrets and deployment credentials and permitting their replacement before the owning job consumes them.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
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  }, {
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    "url" : "https://github.com/nektos/act"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/nektos/act/blob/v0.2.89/cmd/root.go"
  }, {
    "type" : "WEB",
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  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/act-through-missing-authorization-in-the-artifacts-v4-backend"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-321" ],
    "severity" : "HIGH",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-08-24T14:17:02Z"
  }
}