EUVD-2026-63579
GHSA-785c-v4m5-q4wg
Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/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
Network-reachable with no prerequisites; scope change because GITHUB_TOKEN affects external repositories; integrity limited to comment posting only.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/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
Lifecycle Timeline
2DescriptionCVE.org
The github-issue-bot templates in appwrite/templates verify the GitHub webhook signature with an inverted condition. verifyWebhook in node/github-issue-bot/src/github.js and in node-typescript/github-issue-bot/src/github.ts returns "typeof signature !== 'string' || (await verify(...))", so when the X-Hub-Signature-256 header is absent the first operand is true, the logical OR short-circuits, and the function reports success without performing any HMAC verification. main.js rejects a request only when verifyWebhook returns false, so an unauthenticated request carrying no signature passes the check. Processing then continues to postComment, which takes the repository and issue objects directly from the request body, letting the caller direct the deployed function to post a comment on a repository and issue of their choosing using the configured GITHUB_TOKEN, with the issue author login from the body interpolated into the comment text.
AnalysisAI
Webhook signature bypass in the appwrite/templates github-issue-bot (≤ 1.1.2) allows any unauthenticated network caller to invoke the bot's comment-posting functionality without a valid GitHub HMAC signature. An inverted boolean condition in verifyWebhook causes requests lacking the X-Hub-Signature-256 header to short-circuit to success, so the body is processed as if it were a legitimate GitHub event. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | The github-issue-bot template must be deployed as a publicly accessible function endpoint with a GITHUB_TOKEN configured with write access to at least one GitHub repository. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 5.8 with vector AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N is appropriate: the attack is trivially executable over the network without credentials or complexity, and the Scope:Changed metric reflects that the configured GITHUB_TOKEN is leveraged to affect GitHub repositories outside the vulnerable application boundary. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker sends an HTTP POST to the publicly accessible github-issue-bot function endpoint, omitting the X-Hub-Signature-256 header and supplying a JSON body with attacker-chosen 'repository', 'issue', and 'sender.login' fields. The inverted condition in verifyWebhook returns true, main.js continues to postComment, and the deployment's GITHUB_TOKEN posts an attacker-crafted comment to the specified GitHub issue. … |
| Remediation | No vendor-released patched version is independently confirmed in the available data - the fix version must be verified by monitoring the upstream repository at https://github.com/appwrite/templates and the tracking issue at https://github.com/appwrite/templates/issues/350. … Detailed patch versions, workarounds, and compensating controls in full report. |
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