CVE-2021-36159Network attack vector

Memory disclosure or crash via truncated FTP response

Published Aug 3, 2021 · Updated Aug 4, 2024

Out-of-bounds read in libfetch before 2021-07-26 allows remote attackers to read process memory or crash a client via an FTP response. The FTP passive-mode parser uses strtol to place response numbers into address bytes, then checks for the NUL terminator only after advancing past a prematurely ended line. Exploitation requires a client to process a truncated passive-mode reply from an attacker-controlled FTP server, limiting the result to memory disclosure or a client crash.

CVSS severity9.1
Critical
EPSS probability2.64%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in libfetch before 2021-07-26 allows remote attackers to read process memory or crash a client via an FTP response. The FTP passive-mode parser uses strtol to place response numbers into address bytes, then checks for the NUL terminator only after advancing past a prematurely ended line. Exploitation requires a client to process a truncated passive-mode reply from an attacker-controlled FTP server, limiting the result to memory disclosure or a client crash.

The record

CVE
CVE-2021-36159
Published
Aug 3, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-125, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 3, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
6.4NIST NVDAV:N/AC:L/Au:N/C:P/I:N/A:P

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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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