CVE-2021-46837Network attack vector

Remote crash via malformed T.38 SDP

Published Aug 30, 2022 · Updated Aug 4, 2024

Asterisk res_pjsip_t38 allows remote authenticated users to crash Asterisk via a crafted T.38 re-invite response. The callback appends media relative to the active topology when an m=image line carries port zero, dereferencing invalid session-media state instead of replacing the topology entry. Exploitation requires an authenticated SIP session with T.38 faxing enabled; the consequence is a service crash without demonstrated confidentiality or integrity impact.

CVSS severity6.5
Medium
EPSS probability2.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Asterisk res_pjsip_t38 allows remote authenticated users to crash Asterisk via a crafted T.38 re-invite response. The callback appends media relative to the active topology when an m=image line carries port zero, dereferencing invalid session-media state instead of replacing the topology entry. Exploitation requires an authenticated SIP session with T.38 faxing enabled; the consequence is a service crash without demonstrated confidentiality or integrity impact.

The record

CVE
CVE-2021-46837
Published
Aug 30, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 30, 2022CVE 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Endpoint 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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo