MEDIUM
CVE-2021-31878
CWE-617Published: July 30, 2021· Updated: Jun 17, 2026
6.5
CVSS v3.1
Official Description
An issue was discovered in PJSIP in Asterisk before 16.19.1 and before 18.5.1. To exploit, a re-INVITE without SDP must be received after Asterisk has sent a BYE request.
Technical Analysis
CVE-2021-31878 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
A successful exploit results in availability disruption (denial of service), with a CVSS base score of 6.5.
CVSS v3.1 Vector Breakdown
Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.Low
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Affected Vendors & Products
digium1 product(s)
asterisk
Source: NVD CPE · 6 total CPE entries
Exploit & PoC Resources
NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.
Official Patches & Advisories
All References (10)
→
http://downloads.asterisk.org/pub/security/AST-2021-007.htmlPatch · Vendor Advisory
→
http://packetstormsecurity.com/files/163638/Asterisk-Project-Security-Advisory-AST-2021-007.htmlPatch · Third Party Advisory · VDB Entry
→
http://seclists.org/fulldisclosure/2021/Jul/48Mailing List · Patch · Third Party Advisory
→
https://downloads.digium.com/pub/security/AST-2021-007.htmlPatch · Vendor Advisory
→
https://issues.asterisk.org/jira/browse/ASTERISK-29381Exploit · Issue Tracking · Vendor Advisory
→
http://downloads.asterisk.org/pub/security/AST-2021-007.htmlPatch · Vendor Advisory
→
http://packetstormsecurity.com/files/163638/Asterisk-Project-Security-Advisory-AST-2021-007.htmlPatch · Third Party Advisory · VDB Entry
→
http://seclists.org/fulldisclosure/2021/Jul/48Mailing List · Patch · Third Party Advisory
→
https://downloads.digium.com/pub/security/AST-2021-007.htmlPatch · Vendor Advisory
→
https://issues.asterisk.org/jira/browse/ASTERISK-29381Exploit · Issue Tracking · Vendor Advisory
Quick Facts
CVE IDCVE-2021-31878
CVSS Score6.5 / 10
SeverityMEDIUM
WeaknessCWE-617
CISA KEVNo
Affected1 vendor(s)
PublishedJul 30, 2021
Related CVEs (CWE-617)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-31878 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.