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Fix GH-23453: bad free with a context engine ID longer than 32 bytes #23456

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Fix GH-23453: bad free with a context engine ID longer than 32 bytes #23456

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dc6305a
Fix GH-23453: bad free with a context engine ID longer than 32 bytes
lazerg Aug 25, 2026
afd9fc4
Use a behavioural description in the GH-23453 test title
lazerg Aug 25, 2026
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4 changes: 4 additions & 0 deletions NEWS
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,10 @@ PHP NEWS
. Fixed a leak when a persistent connection failed a liveness check
with no other live PDO handle. (iliaal)

- SNMP:
. Fixed bug GH-23453 (SNMP::setSecurity() frees a non-malloced address with a
context engine ID longer than 32 bytes). (Lazizbek Ergashev)

- Standard:
. Fixed a memory leak in array_merge_recursive() when the recursive merge of
an object converted to an array fails. (David Carlier)
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3 changes: 2 additions & 1 deletion ext/snmp/snmp.c
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Expand Up @@ -1086,7 +1086,8 @@ static bool netsnmp_session_set_contextEngineID(struct snmp_session *s, zend_str
size_t ebuf_len = 32, eout_len = 0;
uint8_t *ebuf = (uint8_t *) emalloc(ebuf_len);

if (!snmp_hex_to_binary(&ebuf, &ebuf_len, &eout_len, 1, ZSTR_VAL(contextEngineID))) {
/* Disallow reallocation: ebuf comes from emalloc() and net-snmp would realloc() it. */
if (!snmp_hex_to_binary(&ebuf, &ebuf_len, &eout_len, 0, ZSTR_VAL(contextEngineID))) {
// TODO Promote to Error?
php_error_docref(NULL, E_WARNING, "Bad engine ID value '%s'", ZSTR_VAL(contextEngineID));
efree(ebuf);
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17 changes: 17 additions & 0 deletions ext/snmp/tests/gh23453.phpt
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@@ -0,0 +1,17 @@
--TEST--
GH-23453 (SNMP::setSecurity() frees a non-malloced address with a context engine ID longer than 32 bytes)
--EXTENSIONS--
snmp
--FILE--
<?php
$session = new SNMP(SNMP::VERSION_3, 'localhost', 'user');

// 32 bytes is the maximum length of a context engine ID
var_dump($session->setSecurity('authPriv', 'SHA', 'authpassword12345', 'AES', 'privpassword12345', 'myContext', str_repeat('aa', 32)));
var_dump($session->setSecurity('authPriv', 'SHA', 'authpassword12345', 'AES', 'privpassword12345', 'myContext', str_repeat('aa', 33)));
?>
--EXPECTF--
bool(true)

Warning: SNMP::setSecurity(): Bad engine ID value 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa' in %s on line %d
bool(false)
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