CVE-2021-43804Network attack vector

Out-of-bounds read via unchecked RTCP reason length

Published Dec 22, 2021 · Updated Nov 4, 2025

Out-of-bounds read in PJSIP PJPROJECT 2.11.1 and earlier allows remote attackers to read past an RTCP BYE packet via an invalid reason length. The parse_rtcp_bye function copies the reason into peer_sdes_buf_ using the packet-declared byte count without first limiting it to the bytes actually received. Any application using PJMEDIA with RTCP enabled is exposed; published sources do not establish whether the read discloses data or only interrupts the process.

CVSS severity7.3
High
EPSS probability2.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in PJSIP PJPROJECT 2.11.1 and earlier allows remote attackers to read past an RTCP BYE packet via an invalid reason length. The parse_rtcp_bye function copies the reason into peer_sdes_buf_ using the packet-declared byte count without first limiting it to the bytes actually received. Any application using PJMEDIA with RTCP enabled is exposed; published sources do not establish whether the read discloses data or only interrupts the process.

The record

CVE
CVE-2021-43804
Published
Dec 22, 2021
Updated
Nov 4, 2025
Vendor
PJSIP
Product
PJPROJECT
Classifications
CWE-125
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 22, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 4, 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=<= 2.11.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

PJSIP · PJPROJECTversion=<= 2.11.1

Published CVSS scores

7.3NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
7.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

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-125Out-of-bounds Read

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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