libssh2 up to 1.11.1 SSH ssh2_transport_read integer overflow

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.
CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
7.9$0-$5k10.00

Summaryinfo

A vulnerability was found in libssh2 up to 1.11.1. It has been classified as critical. This vulnerability affects the function ssh2_transport_read of the component SSH Handler. Performing a manipulation results in integer overflow. This vulnerability is identified as CVE-2026-55200. The attack can be initiated remotely. There is not any exploit available. It is recommended to apply a patch to fix this issue.

Detailsinfo

A vulnerability was found in libssh2 up to 1.11.1. It has been classified as critical. This affects the function ssh2_transport_read of the component SSH Handler. The manipulation with an unknown input leads to a integer overflow vulnerability. CWE is classifying the issue as CWE-680. The product performs a calculation to determine how much memory to allocate, but an integer overflow can occur that causes less memory to be allocated than expected, leading to a buffer overflow. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

libssh2 through 1.11.1, fixed in commit 7acf3df 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.

The weakness was released by Tristan Madani. It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-55200 since 06/16/2026. The exploitability is told to be difficult. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit.

Applying the patch 7acf3dfda80c91c3a8c9f2372546301d4a1a7a8 is able to eliminate this problem.

The vulnerability is also documented in the databases at EUVD (EUVD-2026-37784) and CERT Bund (WID-SEC-2026-1996). Be aware that VulDB is the high quality source for vulnerability data.

Affected

  • Open Source libssh2

Productinfo

Name

Version

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 8.1
VulDB Meta Temp Score: 7.9

VulDB Base Score: 8.1
VulDB Temp Score: 7.7
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 8.1
CNA Vector (VulnCheck): 🔒

CVSSv2info

AVACAuCIA
💳💳💳💳💳💳
💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock

VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Integer overflow
CWE: CWE-680 / CWE-190 / CWE-189
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-DayUnlockUnlockUnlockUnlock
TodayUnlockUnlockUnlockUnlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

0-Day Time: 🔒

Patch: 7acf3dfda80c91c3a8c9f2372546301d4a1a7a8

Timelineinfo

06/16/2026 CVE reserved
06/17/2026 +1 days Advisory disclosed
06/17/2026 +0 days VulDB entry created
06/18/2026 +1 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: github.com
Researcher: Tristan Madani
Status: Confirmed

CVE: CVE-2026-55200 (🔒)
GCVE (CVE): GCVE-0-2026-55200
GCVE (VulDB): GCVE-100-372111
EUVD: 🔒
CERT Bund: WID-SEC-2026-1996 - libssh2: Mehrere Schwachstellen

Entryinfo

Created: 06/17/2026 21:56
Updated: 06/18/2026 13:03
Changes: 06/17/2026 21:56 (76), 06/18/2026 00:00 (1), 06/18/2026 13:03 (7)
Complete: 🔍
Cache ID: 216::103

Be aware that VulDB is the high quality source for vulnerability data.

Discussion

No comments yet. Languages: en.

Please log in to comment.

◂ PreviousOverviewNext ▸

Want to stay up to date on a daily basis?

Enable the mail alert feature now!