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MIT krb5 Security Advisory 2011-004 Original release: 2011-04-12 Last update: 2011-04-12
Topic: kadmind invalid pointer free()
CVSSv2 Vector: AV:N/AC:L/Au:N/C:C/I:C/A:C/E:POC/RL:OF/RC:C
CVSSv2 Base Score: 10
Access Vector: Network Access Complexity: Low Authentication: None Confidentiality Impact: Complete Integrity Impact: Complete Availability Impact: Complete
CVSSv2 Temporal Score: 7.8
Exploitability: Proof-of-Concept Remediation Level: Official Fix Report Confidence: Confirmed
The password-changing capability of the MIT krb5 administration daemon (kadmind) has a bug that can cause it to attempt to free() an invalid pointer under certain error conditions. This can cause the daemon to crash or induce the execution of arbitrary code (which is believed to be difficult). No exploit that executes arbitrary code is known to exist, but it is easy to trigger a denial of service manually.
An unauthenticated remote attacker can cause the kadmind to terminate, resulting in a denial of service. The attacker might be able to remotely execute code on the host running kadmind, but exploiting the freeing of an invalid pointer to execute arbitrary code is believed to be difficult.
Some platforms detect attempted freeing of invalid pointers and protectively terminate the process, preventing arbitrary code execution on those platforms.
Workaround: restart the kadmind when it crashes, possibly using an automated monitoring process.
Upcoming releases in the krb5-1.7.x, krb5-1.8.x, and krb5-1.9.x series will contain fixes.
For the krb5-1.9 release, apply the following patch:
diff --git a/src/kadmin/server/schpw.c b/src/kadmin/server/schpw.c index 1124445..0056885 100644 - --- a/src/kadmin/server/schpw.c +++ b/src/kadmin/server/schpw.c @@ -52,6 +52,7 @@ process_chpw_request(context, server_handle, realm, keytab,
ret = 0; rep->length = 0;
rep->data = NULL;
auth_context = NULL; changepw = NULL; @@ -76,8 +77,13 @@ process_chpw_request(context, server_handle, realm, keytab, plen = (ptr++ & 0xff); plen = (plen<<8) | (ptr++ & 0xff);
/ verify version number /
@@ -531,6 +537,10 @@ cleanup: if (local_kaddrs != NULL) krb5_free_addresses(server_handle->context, local_kaddrs);
} krb5_kt_close(server_handle->context, kt);
This patch is also available at
A PGP-signed patch is available at
A PGP-signed patch is available at
This announcement is posted at:
This announcement and related security advisories may be found on the MIT Kerberos security advisory page at:
The main MIT Kerberos web page is at:
CVE: CVE-2011-0285 http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-0285
This bug was initially reported to Debian by Felipe Ortega.
The MIT Kerberos Team security contact address is <email@example.com>. When sending sensitive information, please PGP-encrypt it using the following key:
pub 2048R/56CD8F76 2010-12-29 [expires: 2012-02-01] uid MIT Kerberos Team Security Contact <firstname.lastname@example.org>
The dispatch() function in kadmin/server/schpw.c (which handles the password changing protocol) allocates an uninitialized krb5_data structure for the response packet, expecting process_chpw_request() to fill it in. There is remotely-inducible error one path through process_chpw_request() that can return to dispatch() without initializing the data pointer in the krb5_data structure that is to hold the response packet, which will cause process_tcp_connection() in lib/app-utils/net-server.c to free() an invalid pointer (via kill_tcp_or_rpc_connection()). Password change requests that arrive via UDP will not cause kadmind to free() an invalid pointer.
Releases krb5-1.7 and krb5-1.8 put some of the above-mentioned functions in different source files, but the execution flow is largely identical. Releases prior to krb5-1.7 did not have the TCP kpasswd capability, and are not vulnerable.
2011-04-12 original release
Copyright (C) 2011 Massachusetts Institute of Technology -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.8 (SunOS)
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