The regex wasn't escaping external input

Author: JarLob

actions/ql/lib/codeql/actions/security/OutputClobberingQuery.qll

@@ -196,7 +196,10 @@ class WorkflowCommandClobberingFromFileReadSink extends OutputClobberingSink {
         clobbering_cmd.regexpMatch(["ls", Bash::fileReadCommand()] + "\\s.*") and
         (
           // - run: echo "foo=$(<pr-id.txt)"
-          clobbering_stmt.regexpMatch("echo.*" + clobbering_cmd + ".*")
+          exists(string echo, int echoOffset |
+            echo = clobbering_stmt.regexpFind("\\becho\\s+", _, echoOffset) and
+            clobbering_stmt.indexOf(clobbering_cmd, 0, echoOffset + echo.length()) >= 0
+          )
           or
           // A file content is printed to stdout
           // - run: cat pr-id.txt

actions/ql/src/change-notes/2026-07-28-output-clobbering-regex.md

@@ -0,0 +1,4 @@
+---
+category: fix
+---
+* Fixed a performance issue in the `actions/output-clobbering/high` query caused by using unescaped source-code input in a regular expression.

actions/ql/test/query-tests/Security/CWE-074/.github/workflows/output2.yml

@@ -114,3 +114,13 @@ jobs:
         run: |
           # VULNERABLE: halt_error emits its input without JSON encoding
           jq '.value | halt_error(1)' pr-number.json
+      - id: clob18
+        run: |
+          # VULNERABLE: the file name contains regex metacharacters
+          echo "VALUE=$(cat 'pr[number](final).txt')"
+          echo "::set-output name=OUTPUT::SAFE"
+      - id: clob19
+        run: |
+          # VULNERABLE: echo is invoked through env
+          env echo "VALUE=$(cat 'pr[number](final).txt')"
+          echo "::set-output name=OUTPUT::SAFE"

actions/ql/test/query-tests/Security/CWE-074/OutputClobberingHigh.expected

@@ -16,6 +16,8 @@ edges
 | .github/workflows/output2.yml:36:9:41:6 | Uses Step | .github/workflows/output2.yml:106:14:108:51 | # VULNERABLE: raw-output0 emits strings without JSON encoding\njq '.value' --raw-output0 pr-number.json\n | provenance | Config |
 | .github/workflows/output2.yml:36:9:41:6 | Uses Step | .github/workflows/output2.yml:110:14:112:46 | # VULNERABLE: stderr emits its input without JSON encoding\njq '.value \| stderr' pr-number.json\n | provenance | Config |
 | .github/workflows/output2.yml:36:9:41:6 | Uses Step | .github/workflows/output2.yml:114:14:116:53 | # VULNERABLE: halt_error emits its input without JSON encoding\njq '.value \| halt_error(1)' pr-number.json\n | provenance | Config |
+| .github/workflows/output2.yml:36:9:41:6 | Uses Step | .github/workflows/output2.yml:118:14:121:48 | # VULNERABLE: the file name contains regex metacharacters\necho "VALUE=$(cat 'pr[number](final).txt')"\necho "::set-output name=OUTPUT::SAFE"\n | provenance | Config |
+| .github/workflows/output2.yml:36:9:41:6 | Uses Step | .github/workflows/output2.yml:123:14:126:48 | # VULNERABLE: echo is invoked through env\nenv echo "VALUE=$(cat 'pr[number](final).txt')"\necho "::set-output name=OUTPUT::SAFE"\n | provenance | Config |
 nodes
 | .github/workflows/output1.yml:9:18:9:49 | github.event.comment.body | semmle.label | github.event.comment.body |
 | .github/workflows/output1.yml:10:14:13:50 | # VULNERABLE\necho "OUTPUT_1=HARDCODED" >> $GITHUB_OUTPUT\necho "OUTPUT_2=$BODY" >> $GITHUB_OUTPUT\n | semmle.label | # VULNERABLE\necho "OUTPUT_1=HARDCODED" >> $GITHUB_OUTPUT\necho "OUTPUT_2=$BODY" >> $GITHUB_OUTPUT\n |
@@ -39,6 +41,8 @@ nodes
 | .github/workflows/output2.yml:106:14:108:51 | # VULNERABLE: raw-output0 emits strings without JSON encoding\njq '.value' --raw-output0 pr-number.json\n | semmle.label | # VULNERABLE: raw-output0 emits strings without JSON encoding\njq '.value' --raw-output0 pr-number.json\n |
 | .github/workflows/output2.yml:110:14:112:46 | # VULNERABLE: stderr emits its input without JSON encoding\njq '.value \| stderr' pr-number.json\n | semmle.label | # VULNERABLE: stderr emits its input without JSON encoding\njq '.value \| stderr' pr-number.json\n |
 | .github/workflows/output2.yml:114:14:116:53 | # VULNERABLE: halt_error emits its input without JSON encoding\njq '.value \| halt_error(1)' pr-number.json\n | semmle.label | # VULNERABLE: halt_error emits its input without JSON encoding\njq '.value \| halt_error(1)' pr-number.json\n |
+| .github/workflows/output2.yml:118:14:121:48 | # VULNERABLE: the file name contains regex metacharacters\necho "VALUE=$(cat 'pr[number](final).txt')"\necho "::set-output name=OUTPUT::SAFE"\n | semmle.label | # VULNERABLE: the file name contains regex metacharacters\necho "VALUE=$(cat 'pr[number](final).txt')"\necho "::set-output name=OUTPUT::SAFE"\n |
+| .github/workflows/output2.yml:123:14:126:48 | # VULNERABLE: echo is invoked through env\nenv echo "VALUE=$(cat 'pr[number](final).txt')"\necho "::set-output name=OUTPUT::SAFE"\n | semmle.label | # VULNERABLE: echo is invoked through env\nenv echo "VALUE=$(cat 'pr[number](final).txt')"\necho "::set-output name=OUTPUT::SAFE"\n |
 subpaths
 #select
 | .github/workflows/output1.yml:10:14:13:50 | # VULNERABLE\necho "OUTPUT_1=HARDCODED" >> $GITHUB_OUTPUT\necho "OUTPUT_2=$BODY" >> $GITHUB_OUTPUT\n | .github/workflows/output1.yml:9:18:9:49 | github.event.comment.body | .github/workflows/output1.yml:10:14:13:50 | # VULNERABLE\necho "OUTPUT_1=HARDCODED" >> $GITHUB_OUTPUT\necho "OUTPUT_2=$BODY" >> $GITHUB_OUTPUT\n | Potential clobbering of a step output in $@. | .github/workflows/output1.yml:10:14:13:50 | # VULNERABLE\necho "OUTPUT_1=HARDCODED" >> $GITHUB_OUTPUT\necho "OUTPUT_2=$BODY" >> $GITHUB_OUTPUT\n | # VULNERABLE\necho "OUTPUT_1=HARDCODED" >> $GITHUB_OUTPUT\necho "OUTPUT_2=$BODY" >> $GITHUB_OUTPUT\n |
@@ -58,3 +62,5 @@ subpaths
 | .github/workflows/output2.yml:106:14:108:51 | # VULNERABLE: raw-output0 emits strings without JSON encoding\njq '.value' --raw-output0 pr-number.json\n | .github/workflows/output2.yml:36:9:41:6 | Uses Step | .github/workflows/output2.yml:106:14:108:51 | # VULNERABLE: raw-output0 emits strings without JSON encoding\njq '.value' --raw-output0 pr-number.json\n | Potential clobbering of a step output in $@. | .github/workflows/output2.yml:106:14:108:51 | # VULNERABLE: raw-output0 emits strings without JSON encoding\njq '.value' --raw-output0 pr-number.json\n | # VULNERABLE: raw-output0 emits strings without JSON encoding\njq '.value' --raw-output0 pr-number.json\n |
 | .github/workflows/output2.yml:110:14:112:46 | # VULNERABLE: stderr emits its input without JSON encoding\njq '.value \| stderr' pr-number.json\n | .github/workflows/output2.yml:36:9:41:6 | Uses Step | .github/workflows/output2.yml:110:14:112:46 | # VULNERABLE: stderr emits its input without JSON encoding\njq '.value \| stderr' pr-number.json\n | Potential clobbering of a step output in $@. | .github/workflows/output2.yml:110:14:112:46 | # VULNERABLE: stderr emits its input without JSON encoding\njq '.value \| stderr' pr-number.json\n | # VULNERABLE: stderr emits its input without JSON encoding\njq '.value \| stderr' pr-number.json\n |
 | .github/workflows/output2.yml:114:14:116:53 | # VULNERABLE: halt_error emits its input without JSON encoding\njq '.value \| halt_error(1)' pr-number.json\n | .github/workflows/output2.yml:36:9:41:6 | Uses Step | .github/workflows/output2.yml:114:14:116:53 | # VULNERABLE: halt_error emits its input without JSON encoding\njq '.value \| halt_error(1)' pr-number.json\n | Potential clobbering of a step output in $@. | .github/workflows/output2.yml:114:14:116:53 | # VULNERABLE: halt_error emits its input without JSON encoding\njq '.value \| halt_error(1)' pr-number.json\n | # VULNERABLE: halt_error emits its input without JSON encoding\njq '.value \| halt_error(1)' pr-number.json\n |
+| .github/workflows/output2.yml:118:14:121:48 | # VULNERABLE: the file name contains regex metacharacters\necho "VALUE=$(cat 'pr[number](final).txt')"\necho "::set-output name=OUTPUT::SAFE"\n | .github/workflows/output2.yml:36:9:41:6 | Uses Step | .github/workflows/output2.yml:118:14:121:48 | # VULNERABLE: the file name contains regex metacharacters\necho "VALUE=$(cat 'pr[number](final).txt')"\necho "::set-output name=OUTPUT::SAFE"\n | Potential clobbering of a step output in $@. | .github/workflows/output2.yml:118:14:121:48 | # VULNERABLE: the file name contains regex metacharacters\necho "VALUE=$(cat 'pr[number](final).txt')"\necho "::set-output name=OUTPUT::SAFE"\n | # VULNERABLE: the file name contains regex metacharacters\necho "VALUE=$(cat 'pr[number](final).txt')"\necho "::set-output name=OUTPUT::SAFE"\n |
+| .github/workflows/output2.yml:123:14:126:48 | # VULNERABLE: echo is invoked through env\nenv echo "VALUE=$(cat 'pr[number](final).txt')"\necho "::set-output name=OUTPUT::SAFE"\n | .github/workflows/output2.yml:36:9:41:6 | Uses Step | .github/workflows/output2.yml:123:14:126:48 | # VULNERABLE: echo is invoked through env\nenv echo "VALUE=$(cat 'pr[number](final).txt')"\necho "::set-output name=OUTPUT::SAFE"\n | Potential clobbering of a step output in $@. | .github/workflows/output2.yml:123:14:126:48 | # VULNERABLE: echo is invoked through env\nenv echo "VALUE=$(cat 'pr[number](final).txt')"\necho "::set-output name=OUTPUT::SAFE"\n | # VULNERABLE: echo is invoked through env\nenv echo "VALUE=$(cat 'pr[number](final).txt')"\necho "::set-output name=OUTPUT::SAFE"\n |