CVE-2021-34825Network attack vector

Traffic disclosure via fail-open TLS initialization

Published Jun 17, 2021 · Updated Aug 4, 2024

Cleartext transmission in Quassel through 0.13.1 allows remote attackers to read client-core traffic when required TLS initialization fails. The core startup path treats an unusable or missing X.509 certificate as a warning and continues in plaintext-only mode despite --require-ssl. Exposure requires the operator-enabled flag plus a missing, unreadable, or invalid certificate; unauthenticated network attackers can intercept confidential chat traffic.

CVSS severity7.5
High
EPSS probability0.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cleartext transmission in Quassel through 0.13.1 allows remote attackers to read client-core traffic when required TLS initialization fails. The core startup path treats an unusable or missing X.509 certificate as a warning and continues in plaintext-only mode despite --require-ssl. Exposure requires the operator-enabled flag plus a missing, unreadable, or invalid certificate; unauthenticated network attackers can intercept confidential chat traffic.

The record

CVE
CVE-2021-34825
Published
Jun 17, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-319, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 17, 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

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:P/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.

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-319Cleartext Transmission of Sensitive Information
T1557Adversary-in-the-Middle

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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