CVE-2026-55199
Published Jun 17, 2026
Last updated a month ago
- Description
- 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.
- Source
- disclosure@vulncheck.com
- NVD status
- Analyzed
- Products
- libssh2
CVSS 4.0
- Type
- Secondary
- Base score
- 8.2
- Impact score
- -
- Exploitability score
- -
- Vector string
- CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- Severity
- HIGH
CVSS 3.1
- Type
- Primary
- Base score
- 7.5
- Impact score
- 3.6
- Exploitability score
- 3.9
- Vector string
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Severity
- HIGH
- disclosure@vulncheck.com
- CWE-835
- Hype score
- Not currently trending
⚠️ Vulnerabilidades en productos SSH ❗ CVE-2026-55200 ❗ CVE-2026-55199 ❗ CVE-2025-15661 ➡️ Más info: https://t.co/9xhRfNiMrO https://t.co/9p3ghUfVJj
@CERTpy
14 Jul 2026
254 Impressions
1 Retweet
0 Likes
1 Bookmark
0 Replies
0 Quotes
libssh2: CVE-2026-55200 (critical), CVE-2025-15661 (high), CVE-2026-55199 (high) https://t.co/hF8ZpS6vP6 libssh2 CVE-2026-55200 PoC and local RCE scaffold https://t.co/0v2Iymh7l6
@oss_security
25 Jun 2026
853 Impressions
2 Retweets
7 Likes
1 Bookmark
0 Replies
0 Quotes
libssh2 Client-Side Heap-Overflow RCE (CVE-2026-55200) and Pre-Auth DoS (CVE-2026-55199) Direct: https://t.co/bvz86RVZmo https://t.co/0ipkD4wS4E
@NewMaxxSSD
24 Jun 2026
58 Impressions
0 Retweets
0 Likes
0 Bookmarks
0 Replies
0 Quotes
[
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:*",
"matchCriteriaId": "00D62356-F677-41CF-AC66-2871AD2112BA",
"versionEndIncluding": "1.11.1",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
]