CVE-2026-76847
HighCVSS 8.8Exploitation Probability (EPSS)
Low risk13th percentile - higher than 13% 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
- CVE-2026-76133Critical
The affected Ebyte product uses a deprecated hashing algorithm in an authentication-related operation. Under conditions where an attacker can manipulate or predict the authentication exchange, the weak construction may reduce the assurance provided by the authentication mechanism and facilitate unauthorized access.
- CVE-2026-73819Critical
The affected Ebyte product's vendor configuration utility permits access to administrative functions without verifying the operator's identity under certain credential conditions. An unauthenticated attacker on the adjacent network could modify critical settings or change access credentials, potentially preventing legitimate administrators from managing the device.
- CVE-2026-82970Critical
The WP Cookie Notice for GDPR, CCPA & ePrivacy Consent plugin (part of WP Legal Pages) has an unrestricted upload of file with dangerous type vulnerability, allowing the use of malicious files. This issue affects versions from n/a through 4.4.1.
- CVE-2026-59111Critical
An OS command injection vulnerability in the eObčanka-Identifikace application (DIA) on MacOS allows an attacker to register a custom URL scheme (czeeopauth://) for parameterized application execution. Prior to version 3.6.0, incoming URL parameters were passed to the compiled AppleScript wrapper using concatenation without sufficient sanitization.
- CVE-2026-82695Critical
A security flaw has been discovered in Tenda AC18 15.03.05.19. Impacted is an unknown function of the file /goform/telnet of the component Telnet Handler. The manipulation results in missing authentication. The attack can be launched remotely. The exploit has been released to the public and may be used for attacks.
- CVE-2026-82694Critical
A vulnerability was identified in Tenda AC1206 15.03.06.23. This issue affects the function R7WebsSecurityHandler of the file /goform/ate of the component Web UI. The manipulation leads to missing authentication. The attack can be initiated remotely. The exploit is publicly available and might be used.
- CVE-2026-82693Critical
A vulnerability was determined in Tenda AC1206 15.03.06.23. This vulnerability affects the function TendaTelnet of the file /goform/telnet of the component Web UI. Executing a manipulation can lead to missing authentication. It is possible to launch the attack remotely. The exploit has been publicly disclosed and may be utilized.
- CVE-2026-82692Critical
A vulnerability was found in D-Link DNS-340L and DNS-345 up to 20260717. This affects an unknown part of the file /cgi-bin/iscsi_mgr.cgi. Performing a manipulation of the argument alias/username/password/volume_location results in os command injection. It is possible to initiate the attack remotely. The exploit has been made public and could be used.
- CVE-2026-82691Critical
A vulnerability has been found in D-Link DNS-320L, DNS-327L, DNS-340L and DNS-345 up to 20260717. Affected by this issue is some unknown functionality of the file /cgi-bin/usb_device.cgi of the component CGI Handler. Such manipulation of the argument f_ups_ip leads to os command injection. The attack may be performed from remote. The exploit has been disclosed to the public and may be used.
- CVE-2026-82690Critical
A flaw has been found in D-Link DNS-327L and DNS-340L up to 20260717. Affected by this vulnerability is an unknown functionality of the file /cgi-bin/ve_mgr.cgi. This manipulation of the argument f_dev causes os command injection. The attack is possible to be carried out remotely. The exploit has been published and may be used.
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.