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Fencer Vulns
high 7.3

CVE-2021-37706 json

Potential integer underflow upon receiving STUN message in PJSIP

published 2021-12-22 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-24195

cvss
7.3
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
4.9%
EPSS 4.9% chance of exploitation in 30 days, percentile 92%
public exploits
0
none known

Summary

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 affected versions if the incoming STUN message contains an ERROR-CODE attribute, the header length is not checked before performing a subtraction operation, potentially resulting in an integer underflow scenario. This issue affects all users that use STUN. A malicious actor located within the victim’s network may forge and send a specially crafted UDP (STUN) message that could remotely execute arbitrary code on the victim’s machine. Users are advised to upgrade as soon as possible. There are no known workarounds.

Patch / fix

  • asterisk certified_asterisk 16.8.0
  • sangoma asterisk 16.24.1, 18.10.1, 19.2.1
  • ring Debian 12 20230206.0~ds1-1
  • asterisk Debian 14 1:18.10.1~dfsg+~cs6.10.40431411-1

debian advisories DEBIAN-CVE-2021-37706

  • ring Ubuntu 20.04 LTS 20190215.1.f152c98~ds1-1+deb10u2build0.20.04.1
  • ring Ubuntu Pro 18.04 LTS 20180228.1.503da2b~ds1-1ubuntu0.1~esm1
  • pjproject Ubuntu Pro 16.04 LTS 2.1.0.0.ast20130823-1+deb8u1ubuntu0.1~esm1
  • pjproject Ubuntu Pro 18.04 LTS 2.7.2~dfsg-1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2021-37706

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • pjproject Alpine 3.24, Alpine 3.23, Alpine 3.22 +6 more 2.12-r0

alpine advisories ALPINE-CVE-2021-37706

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-37706 updated cvss 7.3

pjproject: Header length is not checked in STUN message ERROR-CODE attribute

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

4.92% chance of exploitation in the next 30 days, higher than 92% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 9.3 AV:N/AC:M/Au:N/C:C/I:C/A:C

Affected products

  • pjsip pjproject

Classification

Weakness
  • CWE-191 Integer Underflow (Wrap or Wraparound)

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.