CVE-2021-26937

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2022-05-24. NVD baseline CVSS 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: ghsa, nvd
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 9%CVSS: 9.8Exploit: NoneExposed: 0

A fix is available — apply it.

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.

CVSS v3
9.8
EG Score
9.8(medium)
EPSS
94.7%
KEV
Not listed

Published

February 9, 2021

Last Modified

May 9, 2025

Advisory Details (9)

Auto-updated Jun 10, 2026
Patch available.
generic

oss-security - Re: screen crash processing combining characters

http://www.openwall.com/lists/oss-security/2021/02/09/8
generic

oss-security - screen crash processing combining characters

https://www.openwall.com/lists/oss-security/2021/02/09/3
generic

[SECURITY] [DSA 4861-1] screen security update

https://www.debian.org/security/2021/dsa-4861
generic

GNU Screen: User-assisted execution of arbitrary code (GLSA 202105-11) — Gentoo security

https://security.gentoo.org/glsa/202105-11
generic

[screen-devel] [bug #60030] Screen segfaults by displaying some UTF-8 ch

https://lists.gnu.org/archive/html/screen-devel/2021-02/msg00000.html
generic

[SECURITY] Fedora 32 Update: screen-4.8.0-5.fc32 - package-announce - Fedora mailing-lists

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JJWLXP45POUUYBJRRWPVAWNZDJTLYWVM/
generic

[SECURITY] Fedora 33 Update: screen-4.8.0-5.fc33 - package-announce - Fedora mailing-lists

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GNWBOIDEPOEQS5RMQVMFKHKXJCGNYWBL/
generic Patch Available

[SECURITY] [DLA 2570-1] screen security update

https://lists.debian.org/debian-lts-announce/2021/02/msg00031.html
generic

Index of /gnu/screen

https://ftp.gnu.org/gnu/screen/

Patch Availability(4)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuscreen-udeb (4.8.0-1ubuntu0.1) @ focal2026-05-23ubuntu
ubuntuscreen (4.1.0~20120320gitdb59704-9ubuntu0.1~esm2) @ trusty2026-05-23ubuntu
redhatscreen-0:4.1.0-0.25.20120314git3c2946.el7_7.12022-03-28redhat
redhatscreen-0:4.1.0-0.27.20120314git3c2946.el7_92021-03-08redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

All Vendor Advisories

(5)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 7× in last 7d / 41× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-11 08:25 UTCEPSS rescore
  2. 2026-07-11 08:25 UTCEPSS rescore
  3. 2026-07-09 19:07 UTCEPSS rescore
  4. 2026-07-08 15:12 UTCEPSS rescore
  5. 2026-07-07 13:43 UTCEPSS rescore
  6. 2026-07-06 16:25 UTCEPSS rescore
  7. 2026-07-06 16:25 UTCEPSS rescore
  8. 2026-07-05 02:28 UTCEPSS rescore
  9. 2026-07-04 06:29 UTCEPSS rescore
  10. 2026-07-04 06:29 UTCEPSS rescore
  11. 2026-07-02 16:57 UTCEPSS rescore
  12. 2026-07-01 15:03 UTCEPSS rescore
  13. 2026-06-30 23:20 UTCEPSS rescore
  14. 2026-06-30 23:20 UTCEPSS rescore
  15. 2026-06-29 14:04 UTCEPSS rescore
  16. 2026-06-28 04:54 UTCEPSS rescore
  17. 2026-06-28 04:54 UTCEPSS rescore
  18. 2026-06-27 03:06 UTCEPSS rescore
  19. 2026-06-27 03:06 UTCEPSS rescore
  20. 2026-06-25 13:48 UTCEPSS rescore
  21. 2026-06-25 13:48 UTCEPSS rescore
  22. 2026-06-24 14:03 UTCEPSS rescore
  23. 2026-06-24 14:03 UTCEPSS rescore
  24. 2026-06-24 12:48 UTCOSV refresh
  25. 2026-06-23 21:31 UTCEPSS rescore
Show 50 more
  1. 2026-06-23 21:31 UTCEPSS rescore
  2. 2026-06-22 14:24 UTCEPSS rescore
  3. 2026-06-22 14:24 UTCEPSS rescore
  4. 2026-06-21 14:55 UTCEPSS rescore
  5. 2026-06-21 14:54 UTCEPSS rescore
  6. 2026-06-21 01:58 UTCEPSS rescore
  7. 2026-06-21 01:58 UTCEPSS rescore
  8. 2026-06-18 17:51 UTCEPSS rescore
  9. 2026-06-18 17:51 UTCEPSS rescore
  10. 2026-06-17 17:51 UTCEPSS rescore
  11. 2026-06-16 17:51 UTCEPSS rescore
  12. 2026-06-15 17:46 UTCEPSS rescore
  13. 2026-06-14 23:15 UTCEPSS rescore
  14. 2026-06-13 22:58 UTCEPSS rescore
  15. 2026-06-13 22:58 UTCEPSS rescore
  16. 2026-06-12 23:10 UTCEPSS rescore
  17. 2026-06-11 13:58 UTCEPSS rescore
  18. 2026-06-10 22:16 UTCEPSS rescore
  19. 2026-06-10 13:20 UTCEPSS rescore
  20. 2026-06-07 17:16 UTCOSV refresh
  21. 2026-06-07 15:23 UTCEPSS rescore
  22. 2026-06-07 15:23 UTCEPSS rescore
  23. 2026-06-06 13:46 UTCEPSS rescore
  24. 2026-06-06 13:46 UTCEPSS rescore
  25. 2026-06-06 13:46 UTCEPSS rescore
  26. 2026-06-05 22:45 UTCEPSS rescore
  27. 2026-06-05 22:45 UTCEPSS rescore
  28. 2026-06-05 06:09 UTCEPSS rescore
  29. 2026-06-05 06:09 UTCEPSS rescore
  30. 2026-06-04 13:10 UTCEPSS rescore
  31. 2026-06-04 13:10 UTCEPSS rescore
  32. 2026-06-02 20:11 UTCEPSS rescore
  33. 2026-06-02 20:11 UTCEPSS rescore
  34. 2026-06-02 20:11 UTCEPSS rescore
  35. 2026-06-01 13:50 UTCEPSS rescore
  36. 2026-06-01 13:50 UTCEPSS rescore
  37. 2026-05-31 22:29 UTCEPSS rescore
  38. 2026-05-31 22:29 UTCEPSS rescore
  39. 2026-05-31 00:15 UTCEPSS rescore
  40. 2026-05-29 13:42 UTCEPSS rescore
  41. 2026-05-28 13:43 UTCEPSS rescore
  42. 2026-05-28 13:43 UTCEPSS rescore
  43. 2026-05-27 13:39 UTCEPSS rescore
  44. 2026-05-27 13:39 UTCEPSS rescore
  45. 2026-05-26 13:42 UTCEPSS rescore
  46. 2026-05-26 07:17 UTCEPSS rescore
  47. 2026-05-26 07:17 UTCEPSS rescore
  48. 2026-05-23 07:57 UTCEG score recompute
  49. 2026-05-23 07:57 UTCVendor advisory
  50. 2026-05-23 07:57 UTCGHSA enrichment

Frequently asked(5)

What is CVE-2021-26937?
CVE-2021-26937 is a critical vulnerability published on February 9, 2021. 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.
When was CVE-2021-26937 disclosed?
CVE-2021-26937 was first published in the National Vulnerability Database on February 9, 2021, with the most recent update on May 9, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-26937 actively exploited?
CVE-2021-26937 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 94.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-26937?
CVE-2021-26937 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2021-26937?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-26937, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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