CVE-2021-22922Public exploitNetwork attack vector

Altered downloads retained after Metalink hash mismatch

Published Aug 5, 2021 · Updated Apr 16, 2026

Improper input validation in curl 7.27.0 through 7.77.0 allows remote attackers to leave altered Metalink downloads on disk. After a downloaded file fails the Metalink XML hash check, the tool reports the mismatch but neither deletes the file nor retries another mirror. A compromised mirror and user invocation of Metalink are required; the retained file can be mistaken for verified content.

CVSS severity6.5
Medium
EPSS probability4.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in curl 7.27.0 through 7.77.0 allows remote attackers to leave altered Metalink downloads on disk. After a downloaded file fails the Metalink XML hash check, the tool reports the mismatch but neither deletes the file nor retries another mirror. A compromised mirror and user invocation of Metalink are required; the retained file can be mistaken for verified content.

The record

CVE
CVE-2021-22922
Published
Aug 5, 2021
Updated
Apr 16, 2026
Vendor
curl
Product
curl
Classifications
CWE-20, CWE-840, CWE-755
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 5, 2021CVE publishedPublication date reported by the CVE source.
  2. Apr 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=curl 7.27.0 to and including 7.77.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

curl · curlversion=curl 7.27.0 to and including 7.77.0

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

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

Weakness, pattern, technique

CWE-20Improper Input Validation
CWE-840Business Logic Errors
CWE-755Improper Handling of Exceptional Conditions

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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