What’s Vulnerable › Vulnerabilities

CVE-2021-27135

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 7.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-02-10 · updated 2026-06-17

Description

xterm before Patch #366 allows remote attackers to execute arbitrary code or cause a denial of service (segmentation fault) via a crafted UTF-8 combining character sequence.

Affected products

• Debian Linux: 9.0
• Fedoraproject Fedora: 33
• Invisible-Island Xterm: before 366 — fixed in 366

How to fix

Upgrade to a fixed version: Invisible-Island Xterm 366. Check the vendor advisory for mitigations.

References

• http://seclists.org/fulldisclosure/2021/May/52
• http://www.openwall.com/lists/oss-security/2021/02/10/7
• https://access.redhat.com/security/cve/CVE-2021-27135
• https://bugzilla.redhat.com/show_bug.cgi?id=1927559
• https://bugzilla.suse.com/show_bug.cgi?id=1182091
• https://github.com/ThomasDickey/xterm-snapshots/commit/82ba55b8f994ab30ff561a347b82ea340ba7075c
• https://invisible-island.net/xterm/xterm.log.html
• https://lists.debian.org/debian-lts-announce/2021/02/msg00019.html
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/35LK2ZXEIJUOGOA7FV2TJL3L6LFJ4X5S/
• https://news.ycombinator.com/item?id=26524650
• https://security.gentoo.org/glsa/202208-22
• https://www.openwall.com/lists/oss-security/2021/02/09/7

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