CVE-2020-9366: A buffer overflow was found in the way GNU Screen before 4.8.0 treated the special escape OSC 49

Q: How do I fix CVE-2020-9366?

screen: upgrade to 4.8.0. Exact commands for each OS are on this page.

Q: Is CVE-2020-9366 being exploited?

CVE-2020-9366 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2020-9366 affect?

CVE-2020-9366 affects screen. Severity is critical (CVSS 9.8). A buffer overflow was found in the way GNU Screen before 4.8.0 treated the special escape OSC 49. Specially crafted output, or a special program, could corrupt memory and crash Screen or possibly have unspecified other impact.

Q: How urgent is CVE-2020-9366?

Priority 61/100. Critical severity; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2020-9366 is a critical-severity flaw (CVSS 9.8) affecting screen. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A buffer overflow was found in the way GNU Screen before 4.8.0 treated the special escape OSC 49. Specially crafted output, or a special program, could corrupt memory and crash Screen or possibly have unspecified other impact.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.7% (top 14%)
CISA exploited list	No
Weakness	CWE-787
Published	2020-02-24
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: gnu

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-02-24 17:15 UTCPublished CVE record published
2026-06-17 03:27 UTCUpdated Record last modified

gnu screen UPGRADE

Affected: < 4.8.0

Fixed in: 4.8.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy screen || rpm -q screen || screen --version

2. UPGRADE to 4.8.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade screen

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade screen

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-9366?

screen: upgrade to 4.8.0. Exact commands for each OS are on this page.

Is CVE-2020-9366 being exploited?

CVE-2020-9366 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-9366 affect?

CVE-2020-9366 affects screen. Severity is critical (CVSS 9.8). A buffer overflow was found in the way GNU Screen before 4.8.0 treated the special escape OSC 49. Specially crafted output, or a special program, could corrupt memory and crash Screen or possibly have unspecified other impact.

How urgent is CVE-2020-9366?

Priority 61/100. Critical severity; Remotely exploitable, no login, no user action

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CVE-2021-26937 CRITICAL 9.8 UPGRADE MITIGATE encoding.c in GNU Screen through 4.8.0 allows remote attackers to cause a denial of service (invalid write acc
CVE-2017-5618 HIGH 7.8 UPGRADE GNU screen before 4.5.1 allows local users to modify arbitrary files and consequently gain root privileges by

References

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