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## https://sploitus.com/exploit?id=1B3647FF-01BC-52E1-9CD0-11125CB023BD
# CVE-2026-55200 - Critical libssh2 Remote Code Execution Vulnerability
**Critical Pre-Authentication Memory Corruption Vulnerability in libssh2**
---
# Overview
| Field | Detail |
| ----------------------- | ---------------------------------------------------- |
| **CVE** | CVE-2026-55200 |
| **CVSS** | 9.2 Critical |
| **Type** | Out-of-Bounds Write |
| **Component** | libssh2 |
| **Affected Versions** | **Note:** OpenSSH itself does not use libssh2 and is not directly affected.
---
# Exploitation Conditions
| Requirement | Value |
| ----------------- | ------------ |
| Network Access | Required |
| Authentication | Not Required |
| User Interaction | Not Required |
| Attack Complexity | Low |
| Remote Attack | Yes |
---
# ๐ Detection
Security teams should monitor for:
* Unexpected segmentation faults
* Heap corruption events
* Abnormal SSH connection attempts
* Application crashes
* Core dumps involving `ssh2_transport_read()`
* Packet parsing errors in logs
---
## Check Installed Version
### Linux
```bash
pkg-config --modversion libssh2
```
### Debian / Ubuntu
```bash
dpkg -l | grep libssh2
apt-cache policy libssh2-1
```
### RHEL / AlmaLinux / Rocky Linux
```bash
rpm -qa | grep libssh2
dnf info libssh2
```
### Alpine Linux
```bash
apk info | grep libssh2
```
### Find Applications Using libssh2
```bash
ldconfig -p | grep libssh2
```
```bash
find /usr -type f -executable -exec ldd {} \; 2>/dev/null | grep libssh2
```
---
# ๐ก๏ธ Mitigation
## Option 1 - Upgrade Immediately (Recommended)
Upgrade to a version containing:
```text
97acf3dfda80c91c3a8c9f2372546301d4a1a7a8
```
### Ubuntu / Debian
```bash
sudo apt update
sudo apt upgrade libssh2-1
sudo reboot
```
### RHEL / AlmaLinux / Rocky Linux
```bash
sudo dnf update libssh2
sudo reboot
```
### Fedora
```bash
sudo dnf upgrade --refresh libssh2
sudo reboot
```
### Alpine Linux
```bash
apk update
apk upgrade libssh2
```
---
## Option 2 - Restrict SSH Exposure
Until patches are available:
### UFW
```bash
sudo ufw allow from TRUSTED_IP to any port 22
sudo ufw deny 22
```
### iptables
```bash
iptables -A INPUT -p tcp --dport 22 -s TRUSTED_IP -j ACCEPT
iptables -A INPUT -p tcp --dport 22 -j DROP
```
### firewalld
```bash
firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="TRUSTED_IP" port protocol="tcp" port="22" accept'
firewall-cmd --reload
```
---
## Option 3 - Harden Applications
Compile applications with:
```bash
-fstack-protector-strong
-D_FORTIFY_SOURCE=2
-fPIE
-pie
-Wl,-z,relro,-z,now
```
Enable:
```text
โ ASLR
โ Stack Canaries
โ RELRO
โ NX
โ PIE
โ Latest Security Patches
```
---
## Option 4 - Container Isolation
For untrusted workloads:
```bash
docker run \
--read-only \
--cap-drop=ALL \
--security-opt no-new-privileges
```
Additional recommendations:
* seccomp profiles
* AppArmor policies
* SELinux enforcement
* Namespace isolation
---
## Option 5 - Monitoring & Detection
Deploy:
* IDS signatures
* SSH telemetry monitoring
* SIEM alerting
* Crash monitoring
* Network anomaly detection
* Packet size anomaly detection
---
# ๐ Risk Assessment
| Category | Rating |
| ----------------- | ------ |
| Exploitability | High |
| Complexity | Low |
| Authentication | None |
| Remote Attack | Yes |
| Supply Chain Risk | High |
| Internet Exposure | High |
---
# Disclosure Timeline
| Date | Event |
| ---------- | -------------------------------- |
| June 2026 | Vulnerability publicly disclosed |
| June 2026 | Security advisory released |
| June 2026 | Fix commit published |
| June 2026+ | Vendor patches begin shipping |
---
# References
| Resource | Link |
| ----------------- | ---------------------------------------------------------------------------------- |
| NVD | https://nvd.nist.gov/vuln/detail/CVE-2026-55200 |
| libssh2 Project | https://libssh2.org |
| GitHub Repository | https://github.com/libssh2/libssh2 |
| Fix Commit | https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8 |
---
# FAQ
### Is OpenSSH affected?
No. OpenSSH does not use libssh2 internally.
---
### Is this vulnerability pre-authentication?
Yes. The vulnerability can potentially be triggered before authentication.
---
Successful exploitation depends on:
* Heap layout
* Compiler mitigations
* Application context
* Memory protection mechanisms
However, memory corruption vulnerabilities of this class are historically considered highly dangerous.
---
### Is exploitation observed in the wild?
At the time of publication, there are no publicly confirmed reports of active exploitation.
---
# Disclaimer
This repository is intended for **educational and defensive security purposes only**.
Do not use any information or code from this repository on systems you do not own or have explicit written authorization to test.
---
**Patch Early โข Audit Dependencies โข Secure Your Supply Chain** ๐ก๏ธ
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