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🛡️ CVE-2026-55200 — libssh2

🟠 CVSS 8.1 — High ⚠️ Exploit Public CWE-680 NVD
8.1
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: High — the attacker first has to win a race, learn a secret or otherwise prepare the target.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2026-55200 is classified as CWE-680: Integer Overflow to Buffer Overflow. 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.

Affected software

CVE-2026-55200 is recorded against 1 package.

  • libssh2 (fixed in 1.11.1)

Timeline and source

Published on 17 June 2026 and last revised on 14 July 2026. A public exploit is known to exist, which raises the urgency of patching considerably. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com
github.com
www.vulncheck.com
web.archive.org

Other advisories for this package

libssh2 has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-680: Integer Overflow to Buffer Overflow) in other software:

Details

Severity HIGH
CVSS Score 8.1
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE CWE-680
Public Exploit ⚠️ Yes
Source NVD
Published 2026-06-17
Updated 2026-08-20
Modified 2026-07-14

Affected Packages

Software From version Fixed in
libssh2 — 1.11.1

Similar Threats

Exploit Protection

Are you running libssh2?

CVE-2026-55200 carries CVSS 8.1 High rating and a public exploit already exists. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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