Critical remote unauthenticated DoS in widely deployed Cisco enterprise phones; can disrupt org-wide voice communications and is high-profile for IT teams.
CVE-2026-20281
Unauthenticated remote DoS in Cisco IP/Video phones via crafted HTTP packets
Is CVE-2026-20281 being exploited?
Not confirmed. CVE-2026-20281 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.33% probability of exploitation in the next 30 days.
How severe is CVE-2026-20281?
CVE-2026-20281 is rated Critical with a CVSS score of 10.0. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-20281?
Not known from our data. No patch reference has been recorded for CVE-2026-20281, which is not the same as no patch existing — a fix may have shipped without a tagged reference, or after this record was written. The vendor advisory is the only authority on whether a fix exists, and mitigations may be available regardless.
What does CVE-2026-20281 affect?
CVE-2026-20281 affects Cisco Desk Phone 9800 Series (SIP), Cisco IP Phone 7800 Series (SIP), Cisco IP Phone 8800 Series (SIP), Cisco Video Phone 8875 (SIP) — phones must be registered to Unified CM with Web Access enabled. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-20281?
Disable Web Access, restrict network access to phones, apply Cisco patch when available
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote unauthenticated attacker can send crafted HTTP packets to exhaust memory, causing phones to enter DoS and require manual reboot.
Immediate action required
- affected12.1(1)SR1
- affected11.5(1)
- affected10.3(2)
- affected10.2(2)
- affected10.3(1)
- affected10.3(1)SR4
- affected11.0(1)
- affected10.4(1)SR2 3rd Party
- affected11.7(1)
- affected12.1(1)
- affected11.0(0.7) MPP
- affected9.3(4) 3rd Party
- affected12.5(1)SR2
- affected10.2(1)SR1
- affected9.3(4)SR3 3rd Party
- affected10.2(1)
- affected12.5(1)
- affected10.3(1)SR2
- affected11-0-1MSR1-1
- affected10.4(1) 3rd Party
- affected12.5(1)SR1
- affected11.5(1)SR1
- affected10.1(1)SR2
- affected12.0(1)SR2
- affected12.6(1)
- affected10.3(1.11) 3rd Party
- affected12.0(1)
- affected12.0(1)SR1
- affected9.3(3)
- affected12.5(1)SR3
- affected10.3(1)SR4b
- affected9.3(4)SR1 3rd Party
- affected10.3(1)SR5
- affected10.1(1.9)
- affected10.3(1.9) 3rd Party
- affected9.3(4)SR2 3rd Party
- affected10.3(1)SR1
- affected10.3(1)SR3
- affected10.1(1)SR1
- affected12.0(1)SR3
- affected12.6(1)SR1
- affected12.7(1)
- affected10.3(1)SR6
- affected12.8(1)
- affected12.7(1)SR1
- affected11.0(2)SR1
- affected11.0(4)
- affected11.0(2)
- affected11.0(4)SR3
- affected11.0(5)
- affected11.0(3)SR2
- affected11.0(3)SR4
- affected11.0(3)SR3
- affected11.0(2)SR2
- affected11.0(4)SR1
- affected11.0(5)SR3
- affected11.0(3)
- affected11.0(5)SR2
- affected11.0(3)SR6
- affected11.0(5)SR1
- affected11.0(4)SR2
- affected11.0(3)SR1
- affected11.0(3)SR5
- affected11.0(6)
- affected12.8(1)SR1
- affected12.8(1)SR2
- affected14.0(1)
- affected14.0(1)SR1
- affected11.0(6)SR1
- affected10.3(1)SR7
- affected14.0(1)SR2
- affected14.1(1)
- affected14.0(1)SR3
- affected11.0(6)SR2
- affected14.1(1)SR1
- affected14.1(1)SR2
- affected11.0(6)SR4
- affected14.2(1)
- affected14.2(1)SR1
- affected11.0(6)SR5
- affected14.1(1)SR3
- affected14.2(1)SR2
- affected3.1(1)
- affected3.0(1)
- affected2.3(1)
- affected2.3(1)SR1
- affected2.2(1)
- affected2.1(1)
- affected2.0(1)
- affected14.2(1)SR3
- affected3.1(1)SR1
- affected14.3(1)
- affected3.2(1)
- affected14.3(1)SR1
- affected14.2(1)SR4
- affected3.3(1)
- affected11.0(6)SR6
- affected14.3(1)SR2
- affected3.4(1)
- affected14.3(1)SR3
- affected3.5(1)
- affected11.0(6)SR7
- affected3.5(1)SR1
- affected14.4(1)
- affected3.6(1)
- affected4.0(1)
- affected14.4(1)SR1
- affected4.1(1)
- affected14.4(1)SR2
- affected4.1(1)SR1
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.