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commit 00f13ea679958cf784a7174d87b15bb76f07d6cf
Author: Nathan Bossart <[email protected]>
AuthorDate: Mon Aug 10 06:38:37 2026 -0700

    psql: Don't do backquote expansion in \unrestrict.
    
    This oversight in commit 71ea0d6795 allows a malicious server to
    inject shell commands into plain-text dump output that are run at
    restore time on the machine running psql.  To fix, interpret all
    text after \unrestrict until the end of the line as its argument.
    
    Reported-by: Lucas Velgus <[email protected]>
    Reported-by: Filip Janus <[email protected]>
    Reported-by: Daniel Bakker <[email protected]>
    Author: Nathan Bossart <[email protected]>
    Reviewed-by: Robert Haas <[email protected]>
    Reviewed-by: Noah Misch <[email protected]>
    Security: CVE-2026-18408
    Backpatch-through: 14
---
 doc/src/sgml/ref/psql-ref.sgml |  5 +++++
 src/bin/psql/command.c         | 19 +++++++++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/doc/src/sgml/ref/psql-ref.sgml b/doc/src/sgml/ref/psql-ref.sgml
index f7c1ccad02e..74f138b0b0a 100644
--- a/doc/src/sgml/ref/psql-ref.sgml
+++ b/doc/src/sgml/ref/psql-ref.sgml
@@ -3407,6 +3407,11 @@ testdb=&gt; <userinput>\setenv LESS -imx4F</userinput>
         <application>pg_dumpall</application>, and
         <application>pg_restore</application>, but it may be useful elsewhere.
         </para>
+        <para>
+        Unlike most other meta-commands, the entire remainder of the line is
+        always taken to be the argument of <command>\unrestrict</command>, and
+        neither variable interpolation nor backquote expansion are performed.
+        </para>
         </listitem>
       </varlistentry>
 
diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index f72b3c4b234..530a7a4bdf5 100644
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -2286,6 +2286,12 @@ exec_command_restrict(PsqlScanState scan_state, bool 
active_branch,
 
                Assert(!restricted);
 
+               /*
+                * Unlike \unrestrict, this argument may safely undergo 
backquote and
+                * variable expansion: HandleSlashCmds() rejects \restrict in
+                * restricted mode before its argument is scanned, so we only 
get here
+                * when the input could execute such things anyway.
+                */
                opt = psql_scan_slash_option(scan_state, OT_NORMAL, NULL, true);
                if (opt == NULL || opt[0] == '\0')
                {
@@ -2614,14 +2620,23 @@ exec_command_unrestrict(PsqlScanState scan_state, bool 
active_branch,
        if (active_branch)
        {
                char       *opt;
+               size_t          len;
 
-               opt = psql_scan_slash_option(scan_state, OT_NORMAL, NULL, true);
+               opt = psql_scan_slash_option(scan_state, OT_WHOLE_LINE, NULL, 
true);
                if (opt == NULL || opt[0] == '\0')
                {
                        pg_log_error("\\%s: missing required argument", cmd);
                        return PSQL_CMD_ERROR;
                }
 
+               /* strip any trailing spaces and semicolons */
+               len = strlen(opt);
+               while (len > 0 &&
+                          (opt[len - 1] == ';' ||
+                               (isascii((unsigned char) opt[len - 1]) &&
+                                isspace((unsigned char) opt[len - 1]))))
+                       opt[--len] = '\0';
+
                if (!restricted)
                {
                        pg_log_error("\\%s: not currently in restricted mode", 
cmd);
@@ -2639,7 +2654,7 @@ exec_command_unrestrict(PsqlScanState scan_state, bool 
active_branch,
                }
        }
        else
-               ignore_slash_options(scan_state);
+               ignore_slash_whole_line(scan_state);
 
        return PSQL_CMD_SKIP_LINE;
 }


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