CVE-2021-31535

Exploitation

Not assessed. CISA has not published an exploitation assessment for this record, and it is not in the KEV catalog. That is an absence of assessment, not a finding of no risk.

SSVC decision

Not assessed by CISA

EPSS probability

10.63% probability of exploitation activity in the next 30 days.

EPSS percentile

Ranks above 95.4% of scored records. A rank, not a probability.

NVD base score

9.8 (CVSS v3.x), scored by the NVD independently of the CNA.

NVD CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

NVD analysis status

Modified. NVD last modified this record on 2026-06-17.

Red Hat severity

Important. Red Hat's rating for its own products, not a CVSS rating.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

Published

2021-05-27 12:26Z5 YR AGO

Last updated

2024-08-03 23:03Z2 YR AGO

Reserved

2021-04-21

Assigning CNA

mitre

Record state

PUBLISHED

Severity

Not rated by the issuing CNA

CNA CVSS vector

Not published by the issuing CNA

Weaknesses

• CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')Base
• CWE-130Improper Handling of Length Parameter InconsistencyBase

Data version

5.1

Document digest

29421e02b4af6ca0cf0547f8c3818a27d59ead14ebebeb1e7e05af4aab5570f4

• unparalleled.euhttps://unparalleled.eu/publications/2021/advisory-unpar-2021-1.txtx_refsource_MISC
• lists.freedesktop.orghttps://lists.freedesktop.org/archives/xorg/x_refsource_MISC
• www.openwall.com[oss-security] 20210518 libX11 security advisory: May 18, 2021http://www.openwall.com/lists/oss-security/2021/05/18/2mailing-listx_refsource_MLIST
• seclists.org20210520 CVE-2021-31535 libX11 Insufficient Length Checks PoC and Archeologyhttp://seclists.org/fulldisclosure/2021/May/52mailing-listx_refsource_FULLDISC
• packetstormsecurity.comhttp://packetstormsecurity.com/files/162737/libX11-Insufficient-Length-Check-Injection.htmlx_refsource_MISC
• lists.debian.org[debian-lts-announce] 20210524 [SECURITY] [DLA 2666-1] libx11 security updatehttps://lists.debian.org/debian-lts-announce/2021/05/msg00021.htmlmailing-listx_refsource_MLIST
• www.debian.orgDSA-4920https://www.debian.org/security/2021/dsa-4920vendor-advisoryx_refsource_DEBIAN
• security.gentoo.orgGLSA-202105-16https://security.gentoo.org/glsa/202105-16vendor-advisoryx_refsource_GENTOO
• www.openwall.comhttps://www.openwall.com/lists/oss-security/2021/05/18/3x_refsource_MISC
• www.openwall.comhttps://www.openwall.com/lists/oss-security/2021/05/18/2x_refsource_MISC
• unparalleled.euhttps://unparalleled.eu/blog/2021/20210518-using-xterm-to-navigate-the-huge-color-space/x_refsource_MISC
• lists.x.orghttps://lists.x.org/archives/xorg-announce/2021-May/003088.htmlx_refsource_MISC
• gitlab.freedesktop.orghttps://gitlab.freedesktop.org/xorg/lib/libx11/-/commit/8d2e02ae650f00c4a53deb625211a0527126c605x_refsource_MISC
• security.netapp.comhttps://security.netapp.com/advisory/ntap-20210813-0001/x_refsource_CONFIRM
• lists.fedoraproject.orgFEDORA-2021-62bb9998b2https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TEOT4RLB76RVPJQKGGTIKTBIOLHX2NR6/vendor-advisoryx_refsource_FEDORA
• lists.apache.org[kafka-dev] 20210831 Security vulnerabilities in kafka:2.13-2.6.0/2.7.0 docker imagehttps://lists.apache.org/thread.html/r61db8e7dcb56dc000a5387a88f7a473bacec5ee01b9ff3f55308aacc%40%3Cdev.kafka.apache.org%3Emailing-listx_refsource_MLIST
• lists.apache.org[kafka-users] 20210831 Security vulnerabilities in kafka:2.13-2.6.0/2.7.0 docker imagehttps://lists.apache.org/thread.html/r61db8e7dcb56dc000a5387a88f7a473bacec5ee01b9ff3f55308aacc%40%3Cusers.kafka.apache.org%3Emailing-listx_refsource_MLIST
• lists.apache.org[kafka-users] 20210901 Re: [EXTERNAL] Re: Security vulnerabilities in kafka:2.13-2.6.0/2.7.0 docker imagehttps://lists.apache.org/thread.html/rbf4ce74b0d1fa9810dec50ba3ace0caeea677af7c27a97111c06ccb7%40%3Cusers.kafka.apache.org%3Emailing-listx_refsource_MLIST
• lists.apache.org[kafka-dev] 20210901 Re: [EXTERNAL] Re: Security vulnerabilities in kafka:2.13-2.6.0/2.7.0 docker imagehttps://lists.apache.org/thread.html/rbf4ce74b0d1fa9810dec50ba3ace0caeea677af7c27a97111c06ccb7%40%3Cdev.kafka.apache.org%3Emailing-listx_refsource_MLIST