CVE-2021-43611Network attack vector

Application crash via trailing backslash parsing

Published Nov 12, 2021 · Updated Aug 4, 2024

Improper resource handling in Belledonne Belle-sip before 5.0.20 allows remote attackers to crash applications via a crafted SIP From header. belle_sip_string_to_backslash_less_unescaped_string advances past a terminal backslash and reads beyond the display-name string boundary. No authentication or user interaction is required; processing the malformed header can terminate a consuming application such as Linphone.

CVSS severity7.5
High
EPSS probability1.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper resource handling in Belledonne Belle-sip before 5.0.20 allows remote attackers to crash applications via a crafted SIP From header. belle_sip_string_to_backslash_less_unescaped_string advances past a terminal backslash and reads beyond the display-name string boundary. No authentication or user interaction is required; processing the malformed header can terminate a consuming application such as Linphone.

The record

CVE
CVE-2021-43611
Published
Nov 12, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-404, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 12, 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:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

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-404Improper Resource Shutdown or Release
T1499Endpoint Denial of Service

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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