How severe is CVE-2026-55200?

CVE-2026-55200 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-55200 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (50th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-55200?

CVE-2026-55200 affects Libssh2. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-55200?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-55200 have an EU (EUVD) identifier?

Yes. CVE-2026-55200 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-37784.

When was CVE-2026-55200 published?

CVE-2026-55200 was published on 2026-06-17 and last updated on 2026-07-01.

CVE-2026-55200

CVE-2026-55200 is a high-severity vulnerability in Libssh2 with a CVSS 3.x base score of 8.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-680.

Key facts

Severity: High (CVSS 3.x base score 8.1)
CVSS v4: 9.2
EPSS exploit prediction: 1% (50th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-37784
Weakness: CWE-680
Affected product: Libssh2
Published: 2026-06-17
Last modified: 2026-07-01

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.

Frequently asked questions

What is CVE-2026-55200?: 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 severe is CVE-2026-55200?: CVE-2026-55200 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-55200 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (50th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-55200?: CVE-2026-55200 affects Libssh2. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-55200?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-55200 have an EU (EUVD) identifier?: Yes. CVE-2026-55200 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-37784.
When was CVE-2026-55200 published?: CVE-2026-55200 was published on 2026-06-17 and last updated on 2026-07-01.

References

Affected products (1)

cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:*

More vulnerabilities in Libssh2

CVE-2019-3859 — Critical (CVSS 9.1): An out of bounds read flaw was discovered in libssh2 before 1.8.1 in the _libssh2_packet_require and…
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