CVE Intelligence
High Memory corruption exploit reference

CVE-2021-4166 — Out-of-bounds Read in vim/vim

vim is vulnerable to Out-of-bounds Read

Published Dec 25, 2021 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: @huntrdev

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 1.6% (30-day exploitation probability)+11
  • Technical severity (high)+6

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
1.58%
ahead of 75% of scored CVEs · Oct 14, 2026
Affects
Apple
Mac Os X and 7 more
CVSS base
7.1
High · 4 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Documented patch — github.com (NIST National Vulnerability Database)
  • Documented patch — huntr.dev (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Apple Mac Os X, Apple Macos, Debian Debian Linux…).
  2. Apply the fixed version or the patch documented under Remediation.
  3. Exploitation requires user interaction: tighten email/web filtering and warn affected users.
  4. Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Apple Mac Os X version 10.15.7-security_update_2020-001version 10.15.7-security_update_2022-001version 10.15.7-security_update_2021-008version 10.15.7-security_update_2021-007version 10.15.7-security_update_2021-006version 10.15.7-security_update_2021-005version 10.15.7-security_update_2021-004version 10.15.7-security_update_2021-003
and 5 more version 10.15.7-security_update_2021-002version 10.15.7-security_update_2021-001version 10.15.7version 10.15.7-security_update_2022-002version 10.15.7-security_update_2022-003
Vulnerable NIST National Vulnerability Database
Apple Macos version 10.15.7-security_update_2022-004≥ 11.0 and < 11.6.6< 12.3 Vulnerable NIST National Vulnerability Database
Debian Debian Linux version 11.0version 10.0version 9.0 Vulnerable NIST National Vulnerability Database
Fedoraproject Fedora version 35version 34 Vulnerable NIST National Vulnerability Database
Opensuse Factory versions not specified by the source Vulnerable NIST National Vulnerability Database
Red Hat Enterprise Linux version 8.0 Vulnerable NIST National Vulnerability Database
SUSE Linux Enterprise version 12.0version 15.0 Vulnerable NIST National Vulnerability Database
Vim Vim < 8.2.3884 Vulnerable NIST National Vulnerability Database
Vim Vim < 8.2 Vulnerable CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Local
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
7.1 CVSS 3.1 High 1.8 5.2 nvd@nist.gov via NIST National Vulnerability Database
7.1 CVSS 3.1 High — — GitHub, Inc. via GitHub Security Advisories
7.1 CVSS 3.0 High 1.8 5.2 security@huntr.dev via NIST National Vulnerability Database
7.1 CVSS 3.0 High — — @huntrdev via CVE Program (cve.org) e CISA ADP
5.8 CVSS 2.0 Medium 8.6 4.9 nvd@nist.gov via NIST National Vulnerability Database
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-125 · Out-of-bounds Read

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 1.58%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
  • Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
endpoint telemetry (EDR)crash dumps

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · vim/vim/vim
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Fix documented
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 7.1
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Modified
    Oct 13, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 13, 2026 · NIST National Vulnerability Database
  • 2021
  • CVE published
    Dec 25, 2021 · @huntrdev

Source activity

Repeated readings are counted rather than listed.

  • 1× References added · Oct 13, 2026 – Oct 13, 2026
  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

18 on the record

Elsewhere on this site

Apple
every CVE for this vendor
Memory corruption
same class
CWE-125
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-104046 Sssd: sssd: denial of service via incomplete identity provider authentication requests 8d
  • CVE-2026-104045 Sssd: sssd: denial of service via race condition in autofs responder 8d
  • CVE-2026-104047 Sssd: sssd: information disclosure via query injection in entra id lookups 8d
  • CVE-2026-104048 Sssd: sssd: authorization bypass via cross-domain username collision in hbac evaluation 8d
  • CVE-2026-102558 Libsoup: libsoup: heap buffer overflow during websocket receive-buffer growth 16d
  • CVE-2026-102555 Libsoup: libsoup: heap buffer overflow via uninitialized length in data-uri base64 decoding 16d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2021-4166 is "Out-of-bounds Read in vim/vim", rated High. It affects Mac Os X (Apple); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.1 describes technical severity. EPSS 1.58% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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