GHSA-m3c4-prhw-mrx6 CVE-2026-22864
Deno has an incomplete fix for command-injection prevention on Windows — case-insensitive extension bypass
- Severity
- 8.1 / 10
- Critical · CVSS 3.1
- Exploit chance (EPSS)
- 0.67%
- Chance of exploitation in the next 30 days. Higher than 52.10% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-77 Improper Neutralization of Special Elements used in a Command ('Command Injection')
- Fix
2.5.6- Upgrade deno to this version or later
Description
Summary
A prior patch aimed to block spawning Windows batch/shell files by returning an error when a spawned path’s extension matched .bat or .cmd. That check performs a case-sensitive comparison against lowercase literals and therefore can be bypassed when the extension uses alternate casing (for example .BAT, .Bat, etc.).
POC
const command = new Deno.Command('./test.BAT', {
args: ['&calc.exe'],
});
const child = command.spawn();
This causes calc.exe to be launched; see the attached screenshot for evidence.
Patched in CVE-2025-61787 — prevents execution of .bat and .cmd files:
photo_2025-10-10 02 27 23
Bypass of the patched vulnerability: photo_2025-10-10 02 27 25
Impact
The script launches calc.exe on Windows, demonstrating that passing user-controlled arguments to a spawned batch script can result in command-line injection.
Mitigation
Users should update to Deno v2.5.6 or newer.
Affected versions
crates.io
| Package | Vulnerable | Fixed in |
|---|---|---|
| deno | < 2.5.6 |
2.5.6 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
deno crates.io → 2.5.6
- cargo
cargo update -p deno --precise 2.5.6
Severity breakdown
CVSS 3.1 8.1
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Weakness
CWE-77: Improper Neutralization of Special Elements used in a Command ('Command Injection')
The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.
How to prevent it
- Architecture and Design: If at all possible, use library calls rather than external processes to recreate the desired functionality.
- Implementation: If possible, ensure that all external commands called from the program are statically created.
- Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- Operation: Run time: Run time policy enforcement may be used in an allowlist fashion to prevent use of any non-sanctioned commands.
- System Configuration: Assign permissions that prevent the user from accessing/opening privileged files.
References
Advisories
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-x2qc-cmh9-f4hf Deno: Denial of service via non-ASCII bytes in WebSocket response headers | Medium | Also affects deno |
| GHSA-8xpq-cjcf-3wh9 Deno: Permission Bypass via Unicode Normalization Mismatch on macOS (APFS) | High | Also affects deno |
| GHSA-968w-xfqw-vp9q Deno: BYONM module resolution allows `package.json` main path traversal to bypass `--allow-read` restrictions | Medium | Also affects deno |
| GHSA-v8fw-85r8-5m23 Deno: Node TCPWrap numeric hostname aliases bypass --deny-net resolved-IP deny checks | Medium | Also affects deno |
| GHSA-9xg4-qhm4-g43w Deno: Miller-Rabin Primality Test Allows Zero Rounds | High | Also affects deno |
| GHSA-7xh3-mhg9-jcw8 Deno: Command Injection via spawnSync & spawn on Windows | High | Also affects deno |
| GHSA-4c8g-jvcx-v4hv Deno: process.loadEnvFile() bypasses env permission checks and mutates process.env with only read access | Medium | Also affects deno |
| GHSA-83pc-3rw9-qpwj Deno: WebSocket API sandbox bypass via missing post-DNS check | Medium | Also affects deno |
MergeHarbor checks every repository's dependencies against this database, ranks what matters by exploitability and reachability, routes it to the owning team and opens the fix pull request.
Check your repos with MergeHarbor