CVE-2021-37746Network attack vector

Deceptive URI opening via incomplete clicked-link validation

Published Jul 30, 2021 · Updated Aug 4, 2024

URL validation in Claws Mail before 3.18.0 and Sylpheed 3.7.0 and earlier allows remote attackers to open a deceptive URI after a click. textview_uri_security_check in textview.c incorrectly accepts non-URI targets and URIs with trailing content beyond the parser-recognized URI length. A crafted message and recipient interaction are required, and a successful click opens an attacker-controlled destination instead of the link the recipient expects.

CVSS severity6.1
Medium
EPSS probability1.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

URL validation in Claws Mail before 3.18.0 and Sylpheed 3.7.0 and earlier allows remote attackers to open a deceptive URI after a click. textview_uri_security_check in textview.c incorrectly accepts non-URI targets and URIs with trailing content beyond the parser-recognized URI length. A crafted message and recipient interaction are required, and a successful click opens an attacker-controlled destination instead of the link the recipient expects.

The record

CVE
CVE-2021-37746
Published
Jul 30, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-601, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 30, 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

6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
5.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/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 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-601URL Redirection to Untrusted Site ('Open Redirect')
T1204.001Malicious Link

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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