Public exploit available
Public proof-of-concept or exploit code exists (ExploitDB / Metasploit / Nuclei).

CVE-1999-0077 — Reliance on Security Through Obscurity in Cisco IOS

CWE-656 — Reliance on Security Through ObscurityCWE-657 — Violation of Secure Design PrinciplesCWE-342 — Predictable Exact Value from Previous Values11 documents8 sources
Severity
9.3CRITICALNVD
EPSS
12.1%
top 6.16%
CISA KEV
Not in KEV
Exploit
PoC available
Public exploit / PoC exists
Affected products
1
Cisco IOS
Timeline
PublishedSep 6
Latest updateApr 16

Description

The Aztech DSL600EU router, when WAN access to the web interface is disabled, does not properly block inbound traffic on TCP port 80, which allows remote attackers to connect to the web interface by guessing a TCP sequence number, possibly involving spoofing of an ARP packet, a related issue to CVE-1999-0077.

CVSS vector

AV:N/AC:M/C:C/I:C/A:CExploitability: 8.6 | Impact: 10.0

Affected Packages1 packages

▶ciscocisco/ios

🔴Vulnerability Details

2
VulDB
Microsoft Windows NT 4.0 TCP Sequence Number authentication spoofing (EDB-19522 / Nessus ID 10443)↗2026-04-16
▶
GHSA
GHSA-w5wj-83wg-9p94: The Aztech DSL600EU router, when WAN access to the web interface is disabled, does not properly block inbound traffic on TCP port 80, which allows rem↗2022-05-01
▶

💥Exploits & PoCs

1
Exploit-DB
Linux Kernel 2.2 - Predictable TCP Initial Sequence Number↗1999-09-27
▶

📋Vendor Advisories

3
Cisco
Cisco IOS Software TCP Initial Sequence Number Randomization Improvements↗2001-03-01
▶
Red Hat
CVE-1999-0077: Predictable TCP sequence numbers allow spoofing↗
▶
Cisco
Cisco IOS Software TCP Initial Sequence Number Randomization Improvements↗
▶

📐Framework References

3
CWE
Reliance on Security Through Obscurity↗
▶
CWE
Violation of Secure Design Principles↗
▶
CWE
Predictable Exact Value from Previous Values↗
▶

💬Community

1
Bugzilla
CVE kernel non-issue statements↗2010-05-13
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CVE-1999-0077 — Reliance on Security Through Obscurity | cvebase