How severe is CVE-2016-2563?

CVE-2016-2563 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2016-2563 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 34% (98th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2016-2563?

CVE-2016-2563 primarily affects 9bis Kitty. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2016-2563?

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

When was CVE-2016-2563 published?

CVE-2016-2563 was published on 2016-04-07 and last updated on 2026-06-17.

CVE-2016-2563

CVE-2016-2563 is a critical-severity vulnerability in 9bis Kitty with a CVSS 3.x base score of 9.8. Its EPSS exploit-prediction score of 34% places it in the 98th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-119.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 34% (98th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-119
Affected product: 9bis Kitty
Published: 2016-04-07
Last modified: 2026-06-17

Description

Stack-based buffer overflow in the SCP command-line utility in PuTTY before 0.67 and KiTTY 0.66.6.3 and earlier allows remote servers to cause a denial of service (stack memory corruption) or execute arbitrary code via a crafted SCP-SINK file-size response to an SCP download request.

Frequently asked questions

What is CVE-2016-2563?: Stack-based buffer overflow in the SCP command-line utility in PuTTY before 0.67 and KiTTY 0.66.6.3 and earlier allows remote servers to cause a denial of service (stack memory corruption) or execute arbitrary code via a crafted SCP-SINK file-size response to an SCP download request.
How severe is CVE-2016-2563?: CVE-2016-2563 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2016-2563 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 34% (98th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2016-2563?: CVE-2016-2563 primarily affects 9bis Kitty. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2016-2563?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2016-2563 published?: CVE-2016-2563 was published on 2016-04-07 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:9bis:kitty:*:*:*:*:*:*:*:*
cpe:2.3:a:simon_tatham:putty:*:*:*:*:*:*:*:*

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