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No exploitation reportedFix available

CVE-2021-26937

No exploitation reported by the sources we read.

  • Published2021-02-09
  • WeaknessCWE-88

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2021-02-0920:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-11-03 15:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-26937?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-26937?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Debian debian linux
BranchAffectedFixed in
9.0= 9.0no fix published
10.0= 10.0no fix published
Fedoraproject fedora
BranchAffectedFixed in
32.x= 32no fix published
33.x= 33no fix published
Gnu screen
BranchAffectedFixed in
4.8≤ 4.8.0no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • screenUbuntu:Pro:14.04:LTSall versions · fixed in 4.1.0~20120320gitdb59704-9ubuntu0.1~esm2
  • screenUbuntu:20.04:LTSall versions · fixed in 4.8.0-1ubuntu0.1
  • screenUbuntu:18.04:LTSall versions · fixed in 4.6.2-1ubuntu1.1
  • screenUbuntu:16.04:LTSall versions · fixed in 4.3.1-2ubuntu0.1
  • screenTuxCare:OracleLinux:6all versions · fixed in 4.0.3-20.el6.cloudlinux.els6
  • screenTuxCare:CentOS:6all versions · fixed in 4.0.3-20.el6.cloudlinux.els6
  • screenSUSE:OpenStack Cloud Crowbar 9all versions · fixed in 4.0.4-23.6.1
  • screenSUSE:OpenStack Cloud Crowbar 8all versions · fixed in 4.0.4-23.6.1

62 more package ranges on OSV.dev

Vendor advisories

  • CVE-2021-26937 Red Hat Product Security38 products fixed · 1 known affected

    screen: crash when processing combining chars

    screen as a component of Red Hat Enterprise Linux 6

  • RHSA-2022:1074 Red Hat Product Security11 products fixed

    Red Hat Security Advisory: screen security update

  • RHSA-2021:0742 Red Hat Product Security15 products fixed

    Red Hat Security Advisory: screen security update

Full record on NVD

Fix

  1. Vendor fix Red Hat Product Security RHSA-2022:1074 · 11 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
  2. Workaround from the vendor Red Hat Product Security RHSA-2022:1074 · 11 productsThis flaw is in utf8 processing; if your screen configuration does not enable utf8 (through configuration such as "defencoding utf-8" in .screenrc), you are not vulnerable.
  3. No fix planned, says the vendor Red Hat Product Security CVE-2021-26937 · 1 productOut of support scope

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub
Metasploit modules
none listed
Metasploit Framework

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2021-02-09
Last Modified
2026-06-17
NVD status
Modified
GitHub Advisory
GHSA-pjrj-fmxp-cmc4

Frequently asked questions

What is CVE-2021-26937?

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.

Is CVE-2021-26937 actively exploited?

Active exploitation of CVE-2021-26937 has not been confirmed. Its EPSS score was 9.1% on 2026-11-03, the estimated probability of exploitation in the next 30 days.

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

CVE-2021-26937 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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Sources for this record