CVE-2021-3903Public exploit

Memory corruption via invalid scroll-state tracking

Published Oct 27, 2021 · Updated Aug 3, 2024

Heap-based buffer overflow in Vim before 8.2.3564 allows local users to crash the editor by scrolling in Ex mode without a valid screen. update_topline marks w_botline valid even when no valid screen exists, causing later scrolling code to access invalid heap memory. Exploitation requires Vim to process crafted Ex-mode editing commands; the resulting invalid access can terminate the process or corrupt memory.

CVSS severity7.8
High
EPSS probability0.65%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in Vim before 8.2.3564 allows local users to crash the editor by scrolling in Ex mode without a valid screen. update_topline marks w_botline valid even when no valid screen exists, causing later scrolling code to access invalid heap memory. Exploitation requires Vim to process crafted Ex-mode editing commands; the resulting invalid access can terminate the process or corrupt memory.

The record

CVE
CVE-2021-3903
Published
Oct 27, 2021
Updated
Aug 3, 2024
Vendor
Vim
Product
Vim
Classifications
CWE-122, CWE-787, T1203
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 27, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <8.2.3564

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Vim · Vimversion=unspecified <8.2.3564

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.6NIST NVDAV:L/AC:L/Au:N/C:P/I:P/A:P
7.3Protect AI (formerly huntr.dev)CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
CWE-787Out-of-bounds Write
T1203Exploitation for Client Execution

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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