CVE-2026-95625 in Plugin Updater
Summary
by MITRE • 09/23/2026
The Tauri updater plugin verifies update binaries using minisign signatures, but the signature covers only the raw binary bytes. The update manifest -- which contains the version number, download URL, and signature -- is fetched over TLS but is never itself signed or authenticated. Because the only anti-rollback check compares the manifest's version field against the current version, and that field is unsigned, an attacker who can serve a crafted manifest can force installation of any older signed release without possessing the developer's private key.
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Analysis
by VulDB Data Team • 09/23/2026
The vulnerability in question stems from a critical architectural flaw within the Tauri updater plugin’s update verification process, specifically regarding how integrity and authenticity are established for remote updates. While the system correctly employs minisign to verify the cryptographic signature of the raw binary payload, it fails to extend this authentication mechanism to the accompanying metadata that dictates which version should be installed. The update manifest, a JSON or similar structured file containing essential fields such as the target version number, download URL, and the expected signature hash, is retrieved over TLS but remains unsigned and unauthenticated at the application level. This creates a significant gap in trust boundaries where the transport layer security provides confidentiality and basic integrity against passive eavesdropping, but does not guarantee that the manifest has not been tampered with by an active man-in-the-middle attacker or a compromised CDN node.
The core technical flaw lies in the anti-rollback mechanism’s reliance on the version field within this unsigned manifest. The updater logic compares the version specified in the fetched manifest against the currently installed version to prevent downgrades, which is a standard security practice intended to mitigate certain classes of downgrade attacks. However, because the version string itself is not cryptographically bound to the signature or authenticated via any digital certificate chain, an attacker capable of intercepting and modifying network traffic can simply alter this field without invalidating the binary’s signature. The raw binary remains validly signed by the developer’s private key, so the application accepts it as legitimate content; yet, because the manifest is untrusted, the version check becomes a trivial bypass rather than a robust security control.
This design allows for an arbitrary downgrade attack where an adversary can force the installation of any older release that was previously published and signed by the developer. The attacker does not need access to the private signing key, which remains secure, but instead exploits the lack of manifest authentication to manipulate the updater’s decision-making logic. By serving a crafted manifest with a lower version number than the currently installed one, while pointing to an older binary that still bears a valid signature, the attacker can trick the application into reverting its state. This is particularly dangerous as it may expose users to known vulnerabilities present in previous versions or allow for the installation of malware if an older build was compromised before being signed and published.
From a threat modeling perspective, this vulnerability aligns with CWE-345 Insufficient Verification of Data Authenticity, as the system fails to verify that all relevant data components are authentic and untampered. It also relates closely to CWE-296 Improper Following of a Certificate’s Chain of Trust in the context of update mechanisms, where trust is established for one part of the payload but not its metadata. In terms of MITRE ATT&CK techniques, this flaw facilitates T1498 Network Denial of Service via Update Manipulation or more specifically supports supply chain attacks by allowing an adversary to inject malicious older versions into the distribution pipeline without needing code signing privileges. The attack vector is primarily network-based (T1072) and requires the attacker to have a position in the network path, such as through DNS spoofing, BGP hijacking, or compromising intermediate proxies.
The operational impact of this vulnerability can be severe depending on the application’s sensitivity. If the older version contains critical security patches that were removed or if it lacks protections against recent exploits, users are effectively forced back into a vulnerable state. Furthermore, in scenarios where software updates include new features with different permission models or API behaviors, an attacker could exploit behavioral differences between versions to bypass access controls or trigger unintended side effects. For applications handling sensitive data or performing privileged operations, reverting to an older version might expose the user to previously patched vulnerabilities such as SQL injection, cross-site scripting, or buffer overflows that were addressed in newer releases but are absent in the downgraded binary.
To mitigate this risk, developers must implement a robust signature verification process for the update manifest itself. The most effective solution is to sign the entire manifest file using minisign or another strong digital signature scheme with the same private key used for signing binaries. This ensures that any modification to the version number, URL, or hash will invalidate the signature and cause the updater to reject the update package entirely. Alternatively, developers can employ a Merkle tree structure where both the binary and manifest are hashed together before being signed, ensuring atomic integrity of all metadata associated with the release. Additionally, implementing strict TLS certificate pinning for the update server would prevent man-in-the-middle attacks from altering even unsigned manifests during transit, although this should be viewed as a defense-in-depth measure rather than a primary fix since it does not address the fundamental lack of data authenticity verification within the application logic itself.