CVE-2021-26937
published 2021-02-09CVE-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…
PriorityP346critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EPSS
9.15%
94.7th percentile
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.
Affected
11 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | debian_linux | — | — |
| debian | debian_linux | — | — |
| debian | screen | < screen 4.8.0-5 (bookworm) | screen 4.8.0-5 (bookworm) |
| fedoraproject | fedora | — | — |
| fedoraproject | fedora | — | — |
| gnu | screen | <= 4.8.0 | — |
| gnu | screen | >= 0 < 4.8.0-5 | 4.8.0-5 |
| gnu | screen | >= 0 < 4.8.0-5 | 4.8.0-5 |
| gnu | screen | >= 0 < 4.8.0-5 | 4.8.0-5 |
| gnu | screen | >= 0 < 4.8.0-5 | 4.8.0-5 |
| msrc | cbl2_screen_4.9.1-1_on_cbl_mariner_2.0 | — | — |
CVSS provenance
nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
nvdv2.07.5HIGHAV:N/AC:L/Au:N/C:P/I:P/A:P
osv9.8CRITICAL
vendor_debian9.8CRITICAL
vendor_msrc9.8CRITICAL
vendor_redhat9.8CRITICAL
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Ubuntu
GNU Screen vulnerability
vendor_ubuntu·2021-02-24
CVE-2021-26937 GNU Screen vulnerability
Title: GNU Screen vulnerability
Summary: GNU Screen could be made to crash or run programs if it processed specially
crafted character sequences.
USN-4747-1 fixed a vulnerability in screen. This update provides
the corresponding update for Ubuntu 14.04 ESM.
Original advisory details:
Felix Weinmann discovered that GNU Screen incorrectly handled certain
character sequences. A remote attacker could use this issue to cause GNU
Screen to crash, resulting in a denial of service, or possibly execute
arbitrary code.
Instructions: In general, a standard system update will make all the necessary changes.
Ubuntu
GNU Screen vulnerability
vendor_ubuntu·2021-02-24
CVE-2021-26937 GNU Screen vulnerability
Title: GNU Screen vulnerability
Summary: GNU Screen could be made to crash or run programs if it processed specially
crafted character sequences.
Felix Weinmann discovered that GNU Screen incorrectly handled certain
character sequences. A remote attacker could use this issue to cause GNU
Screen to crash, resulting in a denial of service, or possibly execute
arbitrary code.
Instructions: In general, a standard system update will make all the necessary changes.
Red Hat
screen: crash when processing combining chars
vendor_redhat·2021-02-10·CVSS 9.8
CVE-2021-26937 [CRITICAL] CWE-787 screen: crash when processing combining chars
screen: crash when processing combining chars
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.
A flaw was found in screen. A specially crafted sequence of combining characters could cause an out of bounds write leading to arbitrary code execution. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.
Mitigation: This 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.
Package: screen (Red Hat Enterprise Linux 6) - Out of support scope
Microsoft
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 c
vendor_msrc·2021-02-09·CVSS 9.8
CVE-2021-26937 [CRITICAL] CWE-88 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 c
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.
FAQ: Is Azure Linux the only Microsoft product that includes this open-source library and is therefore potentially affected by this vulnerability?
One of the main benefits to our customers who choose to use the Azure Linux distro is the commitment to keep it up to date with the most recent and most secure versions of the open source libraries with which the distro is composed. Microsoft is committed to transparency in this work which is why we began publishing CSAF/VEX in October 2025. See this blog post for more information. If impact to additional products is identified,
Debian
CVE-2021-26937: screen - encoding.c in GNU Screen through 4.8.0 allows remote attackers to cause a denial...
vendor_debian·2021·CVSS 9.8
CVE-2021-26937 [CRITICAL] CVE-2021-26937: screen - encoding.c in GNU Screen through 4.8.0 allows remote attackers to cause a denial...
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.
Scope: local
bookworm: resolved (fixed in 4.8.0-5)
bullseye: resolved (fixed in 4.8.0-5)
forky: resolved (fixed in 4.8.0-5)
sid: resolved (fixed in 4.8.0-5)
trixie: resolved (fixed in 4.8.0-5)
GHSA
GHSA-pjrj-fmxp-cmc4: encoding
ghsa_unreviewed·2022-05-24
CVE-2021-26937 [CRITICAL] CWE-88 GHSA-pjrj-fmxp-cmc4: encoding
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.
OSV
CVE-2021-26937: encoding
osv·2021-02-09·CVSS 9.8
CVE-2021-26937 [CRITICAL] CVE-2021-26937: encoding
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.
No detection rules found.
No public exploits indexed.
No writeups or analysis indexed.
http://www.openwall.com/lists/oss-security/2021/02/09/8https://ftp.gnu.org/gnu/screen/https://lists.debian.org/debian-lts-announce/2021/02/msg00031.htmlhttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GNWBOIDEPOEQS5RMQVMFKHKXJCGNYWBL/https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JJWLXP45POUUYBJRRWPVAWNZDJTLYWVM/https://lists.gnu.org/archive/html/screen-devel/2021-02/msg00000.htmlhttps://security.gentoo.org/glsa/202105-11https://www.debian.org/security/2021/dsa-4861https://www.openwall.com/lists/oss-security/2021/02/09/3http://www.openwall.com/lists/oss-security/2021/02/09/8https://ftp.gnu.org/gnu/screen/https://lists.debian.org/debian-lts-announce/2021/02/msg00031.htmlhttps://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GNWBOIDEPOEQS5RMQVMFKHKXJCGNYWBL/https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JJWLXP45POUUYBJRRWPVAWNZDJTLYWVM/https://lists.gnu.org/archive/html/screen-devel/2021-02/msg00000.htmlhttps://security.gentoo.org/glsa/202105-11https://security.netapp.com/advisory/ntap-20250509-0004/https://www.debian.org/security/2021/dsa-4861https://www.openwall.com/lists/oss-security/2021/02/09/3
2021-02-09
Published