High Memory corruption

CVE-2026-20281 — Cisco Desk Phone 9800 Series, IP Phone 7800 and 8800 Series, and Video Phone 8875 with SIP Software Denial of Service Vulnerability

A vulnerability in Cisco Desk Phone 9800 Series, Cisco IP Phone 7800 and 8800 Series, and Cisco Video Phone 8875 that are running Cisco Session Initiation Protocol (SIP) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper memory management when an affected device processes HTTP packets. An attacker could exploit this vulnerability by sending a continuous stream of crafted HTTP packets to the device. A successful exploit could allow the attacker to cause the affected device to continuously consume memory, resulting in a DoS condition. A manual reboot of the device is required to recover from this condition. Note: For this vulnerability to be exploitable, the phone must be registered to Cisco Unified Communications Manager (Unified CM) and have Web Access enabled. Web Access is disabled by default.

Published Sep 2, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: cisco

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

Technical severity (high)+6
Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

—

No EPSS score.

Affects

Cisco

Cisco Session Initiation Protocol (SIP) Software

CVSS base

7.5

High · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

Yes

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Cisco Cisco Session Initiation Protocol (SIP) Software).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Cisco	Cisco Session Initiation Protocol (SIP) Software	version 12.1(1)SR1version 11.5(1)version 10.3(2)version 10.2(2)version 10.3(1)version 10.3(1)SR4version 11.0(1)version 10.4(1)SR2 3rd Party and 102 more version 11.7(1)version 12.1(1)version 11.0(0.7) MPPversion 9.3(4) 3rd Partyversion 12.5(1)SR2version 10.2(1)SR1version 9.3(4)SR3 3rd Partyversion 10.2(1)version 12.5(1)version 10.3(1)SR2version 11-0-1MSR1-1version 10.4(1) 3rd Partyversion 12.5(1)SR1version 11.5(1)SR1version 10.1(1)SR2version 12.0(1)SR2version 12.6(1)version 10.3(1.11) 3rd Partyversion 12.0(1)version 12.0(1)SR1version 9.3(3)version 12.5(1)SR3version 10.3(1)SR4bversion 9.3(4)SR1 3rd Partyversion 10.3(1)SR5version 10.1(1.9)version 10.3(1.9) 3rd Partyversion 9.3(4)SR2 3rd Partyversion 10.3(1)SR1version 10.3(1)SR3version 10.1(1)SR1version 12.0(1)SR3version 12.6(1)SR1version 12.7(1)version 10.3(1)SR6version 12.8(1)version 12.7(1)SR1version 11.0(2)SR1version 11.0(4)version 11.0(2)version 11.0(4)SR3version 11.0(5)version 11.0(3)SR2version 11.0(3)SR4version 11.0(3)SR3version 11.0(2)SR2version 11.0(4)SR1version 11.0(5)SR3version 11.0(3)version 11.0(5)SR2version 11.0(3)SR6version 11.0(5)SR1version 11.0(4)SR2version 11.0(3)SR1version 11.0(3)SR5version 11.0(6)version 12.8(1)SR1version 12.8(1)SR2version 14.0(1)version 14.0(1)SR1version 11.0(6)SR1version 10.3(1)SR7version 14.0(1)SR2version 14.1(1)version 14.0(1)SR3version 11.0(6)SR2version 14.1(1)SR1version 14.1(1)SR2version 11.0(6)SR4version 14.2(1)version 14.2(1)SR1version 11.0(6)SR5version 14.1(1)SR3version 14.2(1)SR2version 3.1(1)version 3.0(1)version 2.3(1)version 2.3(1)SR1version 2.2(1)version 2.1(1)version 2.0(1)version 14.2(1)SR3version 3.1(1)SR1version 14.3(1)version 3.2(1)version 14.3(1)SR1version 14.2(1)SR4version 3.3(1)version 11.0(6)SR6version 14.3(1)SR2version 3.4(1)version 14.3(1)SR3version 3.5(1)version 11.0(6)SR7version 3.5(1)SR1version 14.4(1)version 3.6(1)version 4.0(1)version 14.4(1)SR1version 4.1(1)version 14.4(1)SR2version 4.1(1)SR1	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
7.5	CVSS 3.1	High	3.9	3.6	psirt@cisco.com via NIST National Vulnerability Database
7.5	CVSS 3.1	High	—	—	cisco via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (score shown at the top: psirt@cisco.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-401 · Missing Release of Memory after Effective Lifetime

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.

web/proxy/WAF logsnetwork IDS/IPSendpoint telemetry (EDR)crash dumps

Timeline

What happened to this CVE, newest first.

2026
Affected products added · cisco/cisco session initiation protocol (sip) software
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 15, 2026
CVSS changed · 7.5
Oct 15, 2026 · NIST National Vulnerability Database
Source status changed · → Awaiting Analysis
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Sep 2, 2026 · cisco

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

1 on the record

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-phone-dos-txMY
NIST National Vulnerability Database

Elsewhere on this site

Cisco
every CVE for this vendor

Memory corruption
same class

CWE-401
other pages naming this weakness

Related CVEs (same products)

Medium CVE-2025-20351 Cisco Desk Phone 9800 Series, IP Phone 7800 and 8800 Series, and Video Phone 8875 with SIP Firmware Cross-Site Scripting Vulnerability Oct 15, 2025
High CVE-2025-20350 Cisco Desk Phone 9800 Series, IP Phone 7800 and 8800 Series, and Video Phone 8875 with SIP Firmware Denial of Service Vulnerability Oct 15, 2025

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No FIRST EPSS score.
No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-20281 is "Cisco Desk Phone 9800 Series, IP Phone 7800 and 8800 Series, and Video Phone 8875 with SIP Software Denial of Service Vulnerability", rated High. It affects Cisco Session Initiation Protocol (SIP) Software (Cisco); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.5 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

Comments

Moderated technical discussion. Read the community guidelines.

No comments yet.