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AUSCERT External Security Bulletin Redistribution
ESB-2019.4341
libssh2 integer overflow and out of bounds read/write vulnerabilities
15 November 2019
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AusCERT Security Bulletin Summary
---------------------------------
Product: FortiOS
Publisher: FortiGuard Labs
Operating System: Network Appliance
Impact/Access: Execute Arbitrary Code/Commands -- Remote/Unauthenticated
Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2019-3863 CVE-2019-3862 CVE-2019-3861
CVE-2019-3860 CVE-2019-3859 CVE-2019-3858
CVE-2019-3857 CVE-2019-3856 CVE-2019-3855
Reference: ESB-2019.3647
ESB-2019.3194
ESB-2019.2858.2
ESB-2019.2795.2
ESB-2019.2638
Original Bulletin:
https://fortiguard.com/psirt/FG-IR-19-099
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libssh2 integer overflow and out of bounds read/write vulnerabilities
IR Number : FG-IR-19-099
Date : Nov 14, 2019
Risk : 3/5
Impact : Buffer Overflows
CVE ID : CVE-2019-3855, CVE-2019-3856, CVE-2019-3857, CVE-2019-3858,
CVE-2019-3859, CVE-2019-3860, CVE-2019-3861, CVE-2019-3862,
CVE-2019-3863
CVE ID : CVE-2019-3855, CVE-2019-3856, CVE-2019-3857, CVE-2019-3858,
CVE-2019-3859, CVE-2019-3860, CVE-2019-3861, CVE-2019-3862,
CVE-2019-3863
Summary
Multiple integer overflow and out of bounds read/write vulnerabilities in the
SSL VPN web-mode SSH client may allow an unauthenticated attacker to cause the
SSL VPN user session to break (Denial of service) and possibly to run arbitrary
code via specially crafted packets sent from a malicious SSH server.
This concerns the following CVEs on a precaution basis:
* CVE-2019-3855 integer overflow when reading a specially crafted packet
* CVE-2019-3856 integer overflow if the server sent an extremely large number
of keyboard prompts
* CVE-2019-3857 integer overflow when receiving a specially crafted exit signal
message channel packet
* CVE-2019-3858 zero byte allocation when reading a specially crafted SFTP
packet
* CVE-2019-3859 out of bounds reads in _libssh2_packet_require(v)
* CVE-2019-3860 out of bounds reads when processing specially crafted SFTP
packets
* CVE-2019-3861 out of bounds read when processing a specially crafted packet
* CVE-2019-3862 out of bounds read when receiving a specially crafted exit
status message channel packet
* CVE-2019-3863 integer overflow in userauth_keyboard_interactive with a number
of extremely long prompt strings
Impact
Buffer Overflows
Affected Products
FortiOS 6.2.0
FortiOS 6.0.0 to 6.0.6
FortiOS 5.6.0 to 5.6.10
other versions are not impacted.
Solutions
There is no known exploit for these vulnerabilities and the affected FortiOS
code was patched on 5.6.11, 6.0.7 and 6.2.1, by measure of precaution.
Workarounds:
Do not access SSH server using SSH client in SSL VPN web-mode if the remote SSH
server is operating under an untrusted environment.
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