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High severity · published Jun 17, 2026
CVE-2026-55200
libssh2 - Out-of-Bounds Write via Unchecked packet_length in transport.c
8.3
CVSS
3.9%
EPSS
No
On KEV
Description
libssh2 1.11.1, fixed in commit 97acf3d, contains an out-of-bounds write vulnerability in ssh2_transport_read() that fails to enforce upper bounds on packet_length field. Remote attackers can send crafted SSH packets with excessively large packet_length values to corrupt heap memory and achieve remote code execution.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
High
Integrity
High
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)3.9% · higher than 90% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
LI
libssh2 · libssh2
1.11.1; 1c3f1b7da588f2652260285529ec3c1f1125eb4e before 97acf3dfda80c91c3a8c9f2372546301d4a1a7a8 · source: vendor, NVD
Affected product
LI
libssh2
libssh2
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-55200
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-55200
Patch
https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8
Patch
https://github.com/libssh2/libssh2/pull/2052
Third Party Advisory
https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c
Exploit
https://web.archive.org/web/20260623211210/https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc
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