CVE-2026-76847
HighCVSS 8.8Exploitation Probability (EPSS)
Low risk27th percentile - higher than 27% of all known CVEs
Summary
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.
Risk Assessment
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, making signatures forgeable and ambiguous. Additionally, the backend is reachable from the network by default, allowing any client to read, overwrite or delete artifacts of a concurrently running job with no credentials, potentially exposing secrets and deployment credentials.
Recommendation
Apply a patch that restores run ID validation, uses a random HMAC key, and defaults the server address to loopback, and restrict network access to the backend.
Related vulnerabilities
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- CVE-2026-123551Critical
OpenAM from 14.0.0 before 16.1.4 contains an information disclosure vulnerability that allows unauthenticated attackers to read live session tokens from the notification WebSocket. Attackers can bypass the agent-only check through an unvalidated internal forward on legacy Liberty ID-FF endpoints, collecting iPlanetDirectoryPro tokens to hijack user and administrator sessions.
- CVE-2026-123550Critical
OpenAM before 16.1.4 contains an authentication bypass vulnerability in its SAML v2.0 service provider that accepts unsigned assertions on the ECP (PAOS) and HTTP-Artifact bindings when WantAssertionsSigned is false. Unauthenticated remote attackers can submit forged assertions to obtain sessions as any mapped user, including administrators, and hijack single sign-on to dependent applications.
- CVE-2026-123549Critical
OpenAM before 16.1.4 fails to enforce the Valid Creation Attributes list during self-registration, allowing anonymous attackers to set restricted attributes including group membership. Attackers can register through the legacy self-service REST endpoint or User Self-Service flow to join administrative groups and gain full administrative control of OpenAM.
- CVE-2026-124060Critical
A vulnerability was detected in TOTOLINK CA300-PoE version 6.2c.884 in the UploadCustomModule function of the file /cgi-bin/cstecgi.cgi. Manipulation of the File argument results in a buffer overflow. The attack can be launched remotely, and the exploit is now public and may be used.
- CVE-2026-124059Critical
A security vulnerability has been detected in TOTOLINK CA300-PoE 6.2c.884. The function setWiFiWdsAddConfig in the file /cgi-bin/cstecgi.cgi is affected, where manipulation of the ApCliKeyStr argument leads to a buffer overflow. The attack may be initiated remotely, and the exploit has been disclosed publicly and may be used.
- CVE-2026-124058Critical
A weakness has been identified in TOTOLINK CA300-PoE 6.2c.884. The function setWiFiRepeaterConfig in the file /cgi-bin/cstecgi.cgi is affected, where manipulation of the ApCliKeyStr argument can lead to a buffer overflow. The attack can be launched remotely, and the exploit has been made available to the public and could be used for attacks.
- CVE-2026-124057Critical
A security flaw has been discovered in TOTOLINK CA300-PoE 6.2c.884. This impacts the function setWiFiMultipleConfig of the file /cgi-bin/cstecgi.cgi. Manipulation of the argument Key1Str1 results in a buffer overflow. The attack can be initiated remotely. The exploit has been released to the public and may be used for attacks.
- CVE-2026-123966Critical
A vulnerability was found in Tenda AC19 version 16.03.10.07 in the saveParentControlInfo function of the /goform/saveParentControlInfo file. Manipulating the deviceId argument causes a heap-based buffer overflow. The attack can be carried out remotely, and the exploit has been publicly disclosed.
- CVE-2026-120984Critical
A flaw was found in the Keycloak server's client management component. When a client is created or imported with authorization services enabled, the system fails to properly clear an internal session attribute used during setup. An authenticated attacker with client management permissions can bypass security controls and upload a malicious JavaScript policy that executes on the server.
Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS

