Is CVE-2021-26937 in the CISA KEV catalog?

No. CVE-2021-26937 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-26937?

CVE-2021-26937 has a CVSS v3 base score of 9.8 (CRITICAL).

What is the EPSS score for CVE-2021-26937?

CVE-2021-26937 has an EPSS score of 9.15% (95th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-26937?

Upgrade screen on debian 11 to 4.8.0-5 or later. Fixes are available for 2 affected products.

CVE & CISA-KEV Catalog

CVE-2021-26937

CRITICALEPSS 95th pctl

9.8

CVSS v3

NVD

Description

encoding.c in GNU Screen through 4.8.0 allows remote attackers to cause a denial of service (invalid write access and application crash) or possibly have unspecified other impact via a crafted UTF-8 character sequence.

CWE-88

How to fix

Remediation Available

screenDebian

Fixed in:4.8.0-5CVE-2021-26937

screenUbuntu

Fixed in:4.1.0~20120320gitdb59704-9ubuntu0.1~esm2USN-4747-2

Fixed in:4.3.1-2ubuntu0.1USN-4747-1

Fixed in:4.6.2-1ubuntu1.1USN-4747-1

Fixed in:4.8.0-1ubuntu0.1USN-4747-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploit Intelligence

9.15%probability of exploitation in 30 days

95thpercentile

High risk: more likely to be exploited than 95% of all known CVEs.

References

Exploit3

Third-Party Advisory3

Product1

ftp.gnu.org

Other references3

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-05-09.