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No exploitation reportedFix available

CVE-2021-36159

No exploitation reported by the sources we read.

  • Published2021-08-03
  • Fixed in2021-07-26
  • WeaknessCWE-125

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

libfetch before 2021-07-26, as used in apk-tools, xbps, and other products, mishandles numeric strings for the FTP and HTTP protocols. The FTP passive mode implementation allows an out-of-bounds read because strtol is used to parse the relevant numbers into address bytes. It does not check if the line ends prematurely. If it does, the for-loop condition checks for the '\0' terminator one byte too late.

Timeline

dates in UTC
  1. 2021-08-0314:15CVE publishedNVD

Versions per branch

NVD
Freebsd libfetch
BranchAffectedFixed in
2021.x< 2021-07-262021-07-26

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • apk-toolsCleanStartall versions · fixed in 2.12.6-r0
  • apk-toolsAlpine:v3.24all versions · fixed in 2.12.6-r0
  • apk-toolsAlpine:v3.23all versions · fixed in 2.12.6-r0
  • apk-toolsAlpine:v3.22all versions · fixed in 2.12.6-r0
  • apk-toolsAlpine:v3.21all versions · fixed in 2.12.6-r0
  • apk-toolsAlpine:v3.20all versions · fixed in 2.12.6-r0
  • apk-toolsAlpine:v3.19all versions · fixed in 2.12.6-r0
  • apk-toolsAlpine:v3.18all versions · fixed in 2.12.6-r0

8 more package ranges on OSV.dev

Vendor advisories

  • CVE-2021-36159 Red Hat Product Security

    libfetch: an out of boundary read while libfetch uses strtol to parse the relevant numbers into address bytes leads to information leak or crash

Full record on NVD

Fix

  1. Update Freebsd libfetch to 2021-07-26

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Published
2021-08-03
Last Modified
2026-06-17
NVD status
Modified
GitHub Advisory
GHSA-cqp5-89fm-vp89

Frequently asked questions

What is CVE-2021-36159?

libfetch before 2021-07-26, as used in apk-tools, xbps, and other products, mishandles numeric strings for the FTP and HTTP protocols. The FTP passive mode implementation allows an out-of-bounds read because strtol is used to parse the relevant numbers into address bytes. It does not check if the line ends prematurely. If it does, the for-loop condition checks for the '\0' terminator one byte too late.

Is CVE-2021-36159 actively exploited?

Active exploitation of CVE-2021-36159 has not been confirmed. Its EPSS score was 2.6% on 2026-11-08, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-36159?

CVE-2021-36159 has a CVSS v3 base score of 9.1 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H.

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