diff --git a/javascript/ql/lib/change-notes/2025-04-30-shelljs.md b/javascript/ql/lib/change-notes/2025-04-30-shelljs.md
new file mode 100644
index 000000000000..90a5f5a2a308
--- /dev/null
+++ b/javascript/ql/lib/change-notes/2025-04-30-shelljs.md
@@ -0,0 +1,4 @@
+---
+category: minorAnalysis
+---
+* Improved modeling of the [`shelljs`](https://www.npmjs.com/package/shelljs) and [`async-shelljs`](https://www.npmjs.com/package/async-shelljs) libraries by adding support for the `which`, `cmd`, `asyncExec` and `env`.
diff --git a/javascript/ql/lib/ext/shelljs.model.yml b/javascript/ql/lib/ext/shelljs.model.yml
new file mode 100644
index 000000000000..8d2c8db645d8
--- /dev/null
+++ b/javascript/ql/lib/ext/shelljs.model.yml
@@ -0,0 +1,6 @@
+extensions:
+  - addsTo:
+      pack: codeql/javascript-all 
+      extensible: sourceModel
+    data:
+      - ["shelljs", "Member[env]", "environment"]
diff --git a/javascript/ql/lib/semmle/javascript/frameworks/ShellJS.qll b/javascript/ql/lib/semmle/javascript/frameworks/ShellJS.qll
index 9f3eeb6e0dc9..fc0e366df4b8 100644
--- a/javascript/ql/lib/semmle/javascript/frameworks/ShellJS.qll
+++ b/javascript/ql/lib/semmle/javascript/frameworks/ShellJS.qll
@@ -14,7 +14,8 @@ module ShellJS {
       shellJSMember()
           .getMember([
               "exec", "cd", "cp", "touch", "chmod", "pushd", "find", "ls", "ln", "mkdir", "mv",
-              "rm", "cat", "head", "sort", "tail", "uniq", "grep", "sed", "to", "toEnd", "echo"
+              "rm", "cat", "head", "sort", "tail", "uniq", "grep", "sed", "to", "toEnd", "echo",
+              "which", "cmd", "asyncExec"
             ])
           .getReturn()
   }
@@ -99,7 +100,8 @@ module ShellJS {
    */
   private class ShellJSGenericFileAccess extends FileSystemAccess, ShellJSCall {
     ShellJSGenericFileAccess() {
-      name = ["cd", "cp", "touch", "chmod", "pushd", "find", "ls", "ln", "mkdir", "mv", "rm"]
+      name =
+        ["cd", "cp", "touch", "chmod", "pushd", "find", "ls", "ln", "mkdir", "mv", "rm", "which"]
     }
 
     override DataFlow::Node getAPathArgument() { result = this.getAnArgument() }
@@ -111,7 +113,8 @@ module ShellJS {
   private class ShellJSFilenameSource extends FileNameSource, ShellJSCall {
     ShellJSFilenameSource() {
       name = "find" or
-      name = "ls"
+      name = "ls" or
+      name = "which"
     }
   }
 
@@ -151,16 +154,24 @@ module ShellJS {
   }
 
   /**
-   * A call to `shelljs.exec()` modeled as command execution.
+   * A call to `shelljs.exec()`, `shelljs.cmd()`, or `async-shelljs.asyncExec()` modeled as command execution.
    */
   private class ShellJSExec extends SystemCommandExecution, ShellJSCall {
-    ShellJSExec() { name = "exec" }
-
-    override DataFlow::Node getACommandArgument() { result = this.getArgument(0) }
+    ShellJSExec() { name = ["exec", "cmd", "asyncExec"] }
+
+    override DataFlow::Node getACommandArgument() {
+      if name = "cmd"
+      then
+        result = this.getArgument(_) and
+        not result = this.getOptionsArg()
+      else
+        // For exec/asyncExec: only first argument is command
+        result = this.getArgument(0)
+    }
 
     override predicate isShellInterpreted(DataFlow::Node arg) { arg = this.getACommandArgument() }
 
-    override predicate isSync() { none() }
+    override predicate isSync() { name = "cmd" }
 
     override DataFlow::Node getOptionsArg() {
       result = this.getLastArgument() and
diff --git a/javascript/ql/lib/semmle/javascript/security/dataflow/CleartextLoggingCustomizations.qll b/javascript/ql/lib/semmle/javascript/security/dataflow/CleartextLoggingCustomizations.qll
index 5dca4cf1df28..dbb775f99b58 100644
--- a/javascript/ql/lib/semmle/javascript/security/dataflow/CleartextLoggingCustomizations.qll
+++ b/javascript/ql/lib/semmle/javascript/security/dataflow/CleartextLoggingCustomizations.qll
@@ -171,7 +171,7 @@ module CleartextLogging {
 
   /** An access to the sensitive object `process.env`. */
   class ProcessEnvSource extends Source {
-    ProcessEnvSource() { this = NodeJSLib::process().getAPropertyRead("env") }
+    ProcessEnvSource() { this.(ThreatModelSource).getThreatModel() = "environment" }
 
     override string describe() { result = "process environment" }
   }
diff --git a/javascript/ql/lib/semmle/javascript/security/dataflow/IndirectCommandInjectionCustomizations.qll b/javascript/ql/lib/semmle/javascript/security/dataflow/IndirectCommandInjectionCustomizations.qll
index 9dd6ab4b4a91..84c4600fbc03 100644
--- a/javascript/ql/lib/semmle/javascript/security/dataflow/IndirectCommandInjectionCustomizations.qll
+++ b/javascript/ql/lib/semmle/javascript/security/dataflow/IndirectCommandInjectionCustomizations.qll
@@ -29,7 +29,7 @@ module IndirectCommandInjection {
    * A read of `process.env`, considered as a flow source for command injection.
    */
   private class ProcessEnvAsSource extends Source {
-    ProcessEnvAsSource() { this = NodeJSLib::process().getAPropertyRead("env") }
+    ProcessEnvAsSource() { this.(ThreatModelSource).getThreatModel() = "environment" }
 
     override string describe() { result = "environment variable" }
   }
@@ -37,7 +37,7 @@ module IndirectCommandInjection {
   /** Gets a data flow node referring to `process.env`. */
   private DataFlow::SourceNode envObject(DataFlow::TypeTracker t) {
     t.start() and
-    result = NodeJSLib::process().getAPropertyRead("env")
+    result.(ThreatModelSource).getThreatModel() = "environment"
     or
     exists(DataFlow::TypeTracker t2 | result = envObject(t2).track(t2, t))
   }
diff --git a/javascript/ql/src/Security/CWE-295/DisablingCertificateValidation.ql b/javascript/ql/src/Security/CWE-295/DisablingCertificateValidation.ql
index d9f7267d425a..b5e52d7c6c79 100644
--- a/javascript/ql/src/Security/CWE-295/DisablingCertificateValidation.ql
+++ b/javascript/ql/src/Security/CWE-295/DisablingCertificateValidation.ql
@@ -37,7 +37,7 @@ DataFlow::ObjectLiteralNode tlsOptions() { result.flowsTo(tlsInvocation().getAnA
 from DataFlow::PropWrite disable
 where
   exists(DataFlow::SourceNode env |
-    env = NodeJSLib::process().getAPropertyRead("env") and
+    env.(ThreatModelSource).getThreatModel() = "environment" and
     disable = env.getAPropertyWrite("NODE_TLS_REJECT_UNAUTHORIZED") and
     disable.getRhs().mayHaveStringValue("0")
   )
diff --git a/javascript/ql/test/library-tests/frameworks/Shelljs/ShellJS.expected b/javascript/ql/test/library-tests/frameworks/Shelljs/ShellJS.expected
index 003ae3f442f8..5c3c922a84fc 100644
--- a/javascript/ql/test/library-tests/frameworks/Shelljs/ShellJS.expected
+++ b/javascript/ql/test/library-tests/frameworks/Shelljs/ShellJS.expected
@@ -55,14 +55,19 @@ test_FileSystemAccess
 | tst.js:60:1:60:17 | shelljs.cat(file) |
 | tst.js:60:1:60:41 | shelljs ... cement) |
 | tst.js:61:1:61:17 | shelljs.cat(file) |
+| tst.js:65:1:65:19 | shelljs.which(file) |
 test_MissingFileSystemAccess
 test_SystemCommandExecution
 | tst.js:14:1:14:27 | shelljs ... ts, cb) |
 | tst.js:60:1:60:51 | shelljs ... ec(cmd) |
 | tst.js:61:1:61:27 | shelljs ... ec(cmd) |
+| tst.js:63:1:63:37 | shelljs ... ptions) |
+| tst.js:64:1:64:16 | shelljs.cmd(cmd) |
+| tst.js:68:1:68:36 | shelljs ... ts, cb) |
 test_FileNameSource
 | tst.js:15:1:15:26 | shelljs ...  file2) |
 | tst.js:24:1:24:16 | shelljs.ls(file) |
 | tst.js:25:1:25:22 | shelljs ... , file) |
 | tst.js:26:1:26:30 | shelljs ...  file2) |
 | tst.js:27:1:27:24 | shelljs ...  file2) |
+| tst.js:65:1:65:19 | shelljs.which(file) |
diff --git a/javascript/ql/test/library-tests/frameworks/Shelljs/tst.js b/javascript/ql/test/library-tests/frameworks/Shelljs/tst.js
index 9e7905c98477..2bbcd51f5821 100644
--- a/javascript/ql/test/library-tests/frameworks/Shelljs/tst.js
+++ b/javascript/ql/test/library-tests/frameworks/Shelljs/tst.js
@@ -59,3 +59,10 @@ shelljs.uniq(opts, file1, file2);
 
 shelljs.cat(file).sed(regex, replacement).exec(cmd);
 shelljs.cat(file).exec(cmd);
+
+shelljs.cmd(cmd, arg1, arg2, options);
+shelljs.cmd(cmd);
+shelljs.which(file);
+
+const shelljssync = require("async-shelljs");
+shelljssync.asyncExec(cmd, opts, cb);
diff --git a/javascript/ql/test/query-tests/Security/CWE-078/IndirectCommandInjection/IndirectCommandInjection.expected b/javascript/ql/test/query-tests/Security/CWE-078/IndirectCommandInjection/IndirectCommandInjection.expected
index 7c7321845776..9fc6f6b1bc4e 100644
--- a/javascript/ql/test/query-tests/Security/CWE-078/IndirectCommandInjection/IndirectCommandInjection.expected
+++ b/javascript/ql/test/query-tests/Security/CWE-078/IndirectCommandInjection/IndirectCommandInjection.expected
@@ -2,6 +2,9 @@
 | actions.js:4:6:4:29 | process ... _DATA'] | actions.js:4:6:4:16 | process.env | actions.js:4:6:4:29 | process ... _DATA'] | This command depends on an unsanitized $@. | actions.js:4:6:4:16 | process.env | environment variable |
 | actions.js:8:10:8:23 | e['TEST_DATA'] | actions.js:12:6:12:16 | process.env | actions.js:8:10:8:23 | e['TEST_DATA'] | This command depends on an unsanitized $@. | actions.js:12:6:12:16 | process.env | environment variable |
 | actions.js:14:6:14:21 | getInput('data') | actions.js:14:6:14:21 | getInput('data') | actions.js:14:6:14:21 | getInput('data') | This command depends on an unsanitized $@. | actions.js:14:6:14:21 | getInput('data') | GitHub Actions user input |
+| actions.js:18:10:18:40 | 'rm -rf ... 'SOME'] | actions.js:18:22:18:32 | shelljs.env | actions.js:18:10:18:40 | 'rm -rf ... 'SOME'] | This command depends on an unsanitized $@. | actions.js:18:22:18:32 | shelljs.env | environment variable |
+| actions.js:19:10:19:37 | 'rm -rf ... nv.SOME | actions.js:19:22:19:32 | shelljs.env | actions.js:19:10:19:37 | 'rm -rf ... nv.SOME | This command depends on an unsanitized $@. | actions.js:19:22:19:32 | shelljs.env | environment variable |
+| actions.js:20:10:20:32 | 'rm -rf ... ljs.env | actions.js:20:22:20:32 | shelljs.env | actions.js:20:10:20:32 | 'rm -rf ... ljs.env | This command depends on an unsanitized $@. | actions.js:20:22:20:32 | shelljs.env | environment variable |
 | command-line-parameter-command-injection.js:4:10:4:21 | process.argv | command-line-parameter-command-injection.js:4:10:4:21 | process.argv | command-line-parameter-command-injection.js:4:10:4:21 | process.argv | This command depends on an unsanitized $@. | command-line-parameter-command-injection.js:4:10:4:21 | process.argv | command-line argument |
 | command-line-parameter-command-injection.js:8:10:8:36 | "cmd.sh ... argv[2] | command-line-parameter-command-injection.js:8:22:8:33 | process.argv | command-line-parameter-command-injection.js:8:10:8:36 | "cmd.sh ... argv[2] | This command depends on an unsanitized $@. | command-line-parameter-command-injection.js:8:22:8:33 | process.argv | command-line argument |
 | command-line-parameter-command-injection.js:11:14:11:20 | args[0] | command-line-parameter-command-injection.js:10:13:10:24 | process.argv | command-line-parameter-command-injection.js:11:14:11:20 | args[0] | This command depends on an unsanitized $@. | command-line-parameter-command-injection.js:10:13:10:24 | process.argv | command-line argument |
@@ -44,6 +47,9 @@ edges
 | actions.js:7:15:7:15 | e | actions.js:8:10:8:10 | e | provenance |  |
 | actions.js:8:10:8:10 | e | actions.js:8:10:8:23 | e['TEST_DATA'] | provenance |  |
 | actions.js:12:6:12:16 | process.env | actions.js:7:15:7:15 | e | provenance |  |
+| actions.js:18:22:18:32 | shelljs.env | actions.js:18:10:18:40 | 'rm -rf ... 'SOME'] | provenance |  |
+| actions.js:19:22:19:32 | shelljs.env | actions.js:19:10:19:37 | 'rm -rf ... nv.SOME | provenance |  |
+| actions.js:20:22:20:32 | shelljs.env | actions.js:20:10:20:32 | 'rm -rf ... ljs.env | provenance |  |
 | command-line-parameter-command-injection.js:8:22:8:33 | process.argv | command-line-parameter-command-injection.js:8:10:8:36 | "cmd.sh ... argv[2] | provenance |  |
 | command-line-parameter-command-injection.js:10:6:10:33 | args | command-line-parameter-command-injection.js:11:14:11:17 | args | provenance |  |
 | command-line-parameter-command-injection.js:10:6:10:33 | args | command-line-parameter-command-injection.js:12:26:12:29 | args | provenance |  |
@@ -181,6 +187,12 @@ nodes
 | actions.js:8:10:8:23 | e['TEST_DATA'] | semmle.label | e['TEST_DATA'] |
 | actions.js:12:6:12:16 | process.env | semmle.label | process.env |
 | actions.js:14:6:14:21 | getInput('data') | semmle.label | getInput('data') |
+| actions.js:18:10:18:40 | 'rm -rf ... 'SOME'] | semmle.label | 'rm -rf ... 'SOME'] |
+| actions.js:18:22:18:32 | shelljs.env | semmle.label | shelljs.env |
+| actions.js:19:10:19:37 | 'rm -rf ... nv.SOME | semmle.label | 'rm -rf ... nv.SOME |
+| actions.js:19:22:19:32 | shelljs.env | semmle.label | shelljs.env |
+| actions.js:20:10:20:32 | 'rm -rf ... ljs.env | semmle.label | 'rm -rf ... ljs.env |
+| actions.js:20:22:20:32 | shelljs.env | semmle.label | shelljs.env |
 | command-line-parameter-command-injection.js:4:10:4:21 | process.argv | semmle.label | process.argv |
 | command-line-parameter-command-injection.js:8:10:8:36 | "cmd.sh ... argv[2] | semmle.label | "cmd.sh ... argv[2] |
 | command-line-parameter-command-injection.js:8:22:8:33 | process.argv | semmle.label | process.argv |
diff --git a/javascript/ql/test/query-tests/Security/CWE-078/IndirectCommandInjection/actions.js b/javascript/ql/test/query-tests/Security/CWE-078/IndirectCommandInjection/actions.js
index 021715395217..8fb6994a597c 100644
--- a/javascript/ql/test/query-tests/Security/CWE-078/IndirectCommandInjection/actions.js
+++ b/javascript/ql/test/query-tests/Security/CWE-078/IndirectCommandInjection/actions.js
@@ -12,3 +12,10 @@ function test(e) {
 test(process.env); // $ Source
 
 exec(getInput('data')); // $ Alert
+
+function test2(e) {
+    const shelljs = require('shelljs');
+    exec('rm -rf ' + shelljs.env['SOME']); // $ Alert
+    exec('rm -rf ' + shelljs.env.SOME); // $ Alert
+    exec('rm -rf ' + shelljs.env); // $ Alert
+}