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CVE-2021-21375

Crash in receiving updated SDP answer after initial SDP negotiation failed

6.5 MediumFix available

PJSIP is a free and open source multimedia communication library written in C language implementing standard based protocols such as SIP, SDP, RTP, STUN, TURN, and ICE. In PJSIP version 2.10 and earlier, after an initial INVITE has been sent, when two 183 responses are received, with the first one causing negotiation failure, a crash will occur. This results in a denial of service.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
Required

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

2.08%Up 1.3 points since Apr 14, 2021
90%50%10%1%

What each source reports

CVE List Score used 6.5

Crash in receiving updated SDP answer after initial SDP negotiation failed

PJSIP is a free and open source multimedia communication library written in C language implementing standard based protocols such as SIP, SDP, RTP, STUN, TURN, and ICE. In PJSIP version 2.10 and earlier, after an initial INVITE has been sent, when two 183 responses are received, with the first one causing negotiation failure, a crash will occur. This results in a denial of service.

Record
CVE-2021-21375
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Weakness
CWE-400
Updated
2026-11-02
EUVDEUVD-2021-8685 6.5

PJSIP is a free and open source multimedia communication library written in C language implementing standard based protocols such as SIP, SDP, RTP, STUN, TURN, and ICE. In PJSIP version 2.10 and earlier, after an initial INVITE has been sent, when two 183 responses are received, with the first one causing negotiation failure, a crash will occur. This results in a denial of service.

Record
EUVD-2021-8685
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Updated
2026-11-03
NVD 6.5

PJSIP is a free and open source multimedia communication library written in C language implementing standard based protocols such as SIP, SDP, RTP, STUN, TURN, and ICE. In PJSIP version 2.10 and earlier, after an initial INVITE has been sent, when two 183 responses are received, with the first one causing negotiation failure, a crash will occur. This results in a denial of service.

Record
CVE-2021-21375
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
CVSS 2.0
4.3 MediumAV:N/AC:M/Au:N/C:N/I:N/A:P
Weakness
CWE-400, CWE-754
Updated
2026-11-02
OSVALPINE-CVE-2021-21375 6.5

PJSIP is a free and open source multimedia communication library written in C language implementing standard based protocols such as SIP, SDP, RTP, STUN, TURN, and ICE. In PJSIP version 2.10 and earlier, after an initial INVITE has been sent, when two 183 responses are received, with the first one causing negotiation failure, a crash will occur. This results in a denial of service.

Record
ALPINE-CVE-2021-21375
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSV 6.5

PJSIP is a free and open source multimedia communication library written in C language implementing standard based protocols such as SIP, SDP, RTP, STUN, TURN, and ICE. In PJSIP version 2.10 and earlier, after an initial INVITE has been sent, when two 183 responses are received, with the first one causing negotiation failure, a crash will occur. This results in a denial of service.

Record
CVE-2021-21375
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVDEBIAN-CVE-2021-21375 6.5

PJSIP is a free and open source multimedia communication library written in C language implementing standard based protocols such as SIP, SDP, RTP, STUN, TURN, and ICE. In PJSIP version 2.10 and earlier, after an initial INVITE has been sent, when two 183 responses are received, with the first one causing negotiation failure, a crash will occur. This results in a denial of service.

Record
DEBIAN-CVE-2021-21375
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2021-21375 6.5

PJSIP is a free and open source multimedia communication library written in C language implementing standard based protocols such as SIP, SDP, RTP, STUN, TURN, and ICE. In PJSIP version 2.10 and earlier, after an initial INVITE has been sent, when two 183 responses are received, with the first one causing negotiation failure, a crash will occur. This results in a denial of service.

Record
UBUNTU-CVE-2021-21375
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVMGASA-2021-0336 No score

Updated pjproject packages fix a security vulnerability

An issue has been found in pjproject. Due to bad handling of two consecutive crafted answers to an INVITE, the attacker is able to crash the server resulting in a denial of service (CVE-2021-21375).

Record
MGASA-2021-0336
Updated
2026-11-02
OSVMGASA-2021-0337 No score

Updated pjproject packages fix security vulnerabilities

Currently, PJSIP transport can be reused if they have the same IP address

  • port + protocol. However, this is insufficient for secure transport since it lacks remote hostname authentication. The vulnerability allows for an insecure interaction without user awareness. It affects users who need access to connections to different destinations that translate to the same address, and allows man-in-the-middle attack if attacker can route a connection to another destination such as in the case of DNS spoofing (CVE-2020-15260).

An issue has been found in pjproject. Due to bad handling of two consecutive crafted answers to an INVITE, the attacker is able to crash the server resulting in a denial of service (CVE-2021-21375).

Record
MGASA-2021-0337
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
pjproject
Alpine:v3.14
 before 2.11-r0
2.11-r0
pjproject
Alpine:v3.15
 before 2.11-r0
2.11-r0
pjproject
Alpine:v3.16
 before 2.11-r0
2.11-r0
pjproject
Alpine:v3.17
 before 2.11-r0
2.11-r0
pjproject
Alpine:v3.18
 before 2.11-r0
2.11-r0
pjproject
Alpine:v3.19
 before 2.11-r0
2.11-r0
pjproject
Alpine:v3.20
 before 2.11-r0
2.11-r0
pjproject
Alpine:v3.21
 before 2.11-r0
2.11-r0
pjproject
Alpine:v3.22
 before 2.11-r0
2.11-r0
pjproject
Alpine:v3.23
 before 2.11-r0
2.11-r0
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Affected packages
PackageAffectedFixed
pjproject
Alpine:v3.24
 before 2.11-r0
2.11-r0
ring
Debian:12
 before 20210112.2.b757bac~ds1-1
20210112.2.b757bac~ds1-1
pjproject
Debian:9
 before 2.5.5~dfsg-6+deb9u2, plus listed versions
2.5.5~dfsg-62.5.5~dfsg-6+deb9u1
2.5.5~dfsg-6+deb9u2
ring
Debian:9
 before 20161221.2.7bd7d91~dfsg1-1+deb9u1, plus listed versions
20161221.2.7bd7d91~dfsg1-1
20161221.2.7bd7d91~dfsg1-1+deb9u1
pjproject
Mageia:7
 before 2.7.2-1.1.mga7
2.7.2-1.1.mga7
pjproject
Mageia:8
From an advisory covering 2 CVEs
 before 2.10-5.2.mga8
2.10-5.2.mga8
pjproject
Ubuntu:Pro:16.04:LTS
 before 2.1.0.0.ast20130823-1+deb8u1ubuntu0.1~esm1, plus listed versions
2.1.0.0.ast20130823-12.1.0.0.ast20130823-1+deb8u1build0.16.04.1
2.1.0.0.ast20130823-1+deb8u1ubuntu0.1~esm1
pjproject
Ubuntu:Pro:18.04:LTS
 before 2.7.2~dfsg-1ubuntu0.1~esm1, plus listed versions
2.6~dfsg-22.7~dfsg-12.7.1~dfsg-12.7.1~dfsg-1build12.7.2~dfsg-1
2.7.2~dfsg-1ubuntu0.1~esm1

History

History
RecordedChangedSources
affected, facts
aliasesEUVD
first indexedCVE List, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-21375 is a medium vulnerability (CVSS 6.5) in Teluu Pjsip, published March 10, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 2.08%, the 81st percentile. Fixed in pjproject 2.11-r0.

References

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