CVE details
CVE-2026-55199
libssh2 through 1.11.1, fixed in commit 1762685, contains a pre-authentication denial of service vulnerability in the SSH_MSG_EXT_INFO handler in src/packet.c that allows a malicious SSH server to cause a client CPU exhaustion loop by sending a crafted extension count value. A malicious server can set nr_extensions to 0xFFFFFFFF during key exchange, causing the client to spin in a tight CPU loop for over 60 seconds because return values from _libssh2_get_string() are unchecked and the session timeout does not apply to CPU-bound loops.
Matched ports (2)
| Port | Package | Version | Status | Maintainer |
|---|---|---|---|---|
| security/libssh2 | libssh2 | 1.11.1_1,3 | unaddressed | sbz@FreeBSD.org |
| security/linux-c7-libssh2 | linux-c7-libssh2 | 1.8.0_2 | unaddressed | emulation@FreeBSD.org |
Template for a VuXML entry
Range taken from the CVE record, check it before committing. make newentry in security/vuxml creates the vid.
<vuln vid="FIXME (make newentry)">
<topic>FIXME -- FIXME</topic>
<affects>
<package>
<name>libssh2</name>
<range><lt>FIXME</lt></range>
</package>
<package>
<name>linux-c7-libssh2</name>
<range><lt>FIXME</lt></range>
</package>
</affects>
<description>
<body xmlns="http://www.w3.org/1999/xhtml">
<p>libssh2 through 1.11.1, fixed in commit 1762685, contains a
pre-authentication denial of service vulnerability in the
SSH_MSG_EXT_INFO handler in src/packet.c that allows a malicious SSH
server to cause a client CPU exhaustion loop by sending a crafted
extension count value. A malicious server can set nr_extensions to
0xFFFFFFFF during key exchange, causing the client to spin in a tight
CPU loop for over 60 seconds because return values from
_libssh2_get_string() are unchecked and the session timeout does not
apply to CPU-bound loops.</p>
</body>
</description>
<references>
<cvename>CVE-2026-55199</cvename>
<url>https://nvd.nist.gov/vuln/detail/CVE-2026-55199</url>
</references>
<dates>
<discovery>2026-06-17</discovery>
<entry>2026-10-26</entry>
</dates>
</vuln>