CVE-2021-22876Network attack vector

Credential disclosure via unsanitized automatic Referer

Published Apr 1, 2021 · Updated Jun 9, 2025

Information disclosure in curl 7.1.1 through 7.75.0 allows remote attackers to obtain URL credentials through automatic Referer headers. In Curl_follow, libcurl copies the current URL into the automatically generated Referer header without removing embedded usernames or passwords. Exposure requires URL-embedded credentials, redirect following, and automatic Referer generation, which the curl tool enables with --referer ";auto".

CVSS severity5.3
Medium
EPSS probability5.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in curl 7.1.1 through 7.75.0 allows remote attackers to obtain URL credentials through automatic Referer headers. In Curl_follow, libcurl copies the current URL into the automatically generated Referer header without removing embedded usernames or passwords. Exposure requires URL-embedded credentials, redirect following, and automatic Referer generation, which the curl tool enables with --referer ";auto".

The record

CVE
CVE-2021-22876
Published
Apr 1, 2021
Updated
Jun 9, 2025
Vendor
curl
Product
curl
Classifications
CWE-359
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 1, 2021CVE publishedPublication date reported by the CVE source.
  2. Jun 9, 2025Record 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=7.1.1 to and including 7.75.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

curl · curlversion=7.1.1 to and including 7.75.0

Published CVSS scores

6.1SUSECVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:N/A:N
5.3Canonical UbuntuCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
5.3Oracle LinuxCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/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.

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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-359Exposure of Private Personal Information to an Unauthorized Actor

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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