# CVE-1999-0074: TCP/IP Stack sequential port allocation allows spoofing

Source: https://junglewise.ai/threats/cve-1999-0074-tcp-ip-stack-sequential-port-allocation-allows-spoofing  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 1997-07-01. Updated: 2026-05-10  
License: CC BY 4.0 with a link back

CVE-1999-0074 · Severity: medium · CVSS 6.4 · Published 1997-07-01

A flaw in how certain operating systems manage network connections allows for predictable port assignment. This predictability can be exploited by attackers to impersonate trusted systems or intercept data, potentially leading to unauthorized access or the manipulation of network traffic. Organizations using legacy systems with this behavior are at risk of spoofing attacks that bypass standard network trust assumptions.

Technologies: [Freebsd](https://junglewise.ai/threats/technologies/freebsd), [Linux Kernel](https://junglewise.ai/threats/technologies/kernel), [Microsoft Windows Nt](https://junglewise.ai/threats/technologies/windows-nt), [Netbsd](https://junglewise.ai/threats/technologies/netbsd). Vendors: [Freebsd](https://junglewise.ai/threats/vendors/freebsd), [Linux](https://junglewise.ai/threats/vendors/linux), [Microsoft](https://junglewise.ai/threats/vendors/microsoft), [Netbsd](https://junglewise.ai/threats/vendors/netbsd).

## Quick answers

**Is CVE-1999-0074 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-1999-0074 being exploited in the wild.

**How severe is CVE-1999-0074?** Medium severity, with a CVSS score of 6.4, published 1 July 1997.

**Which products and versions are affected?** Freebsd, Linux Kernel, Microsoft Windows Nt, Netbsd. The advisory does not name versions.

**Is there a fix for CVE-1999-0074?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-1999-0074 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-1999-0074?** Check whether you run Freebsd, Linux Kernel, Microsoft Windows Nt or one of the others listed. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability stems from the sequential allocation of TCP ports for listening services, rather than using a randomized or non-predictable selection process. An unauthenticated remote attacker can predict the next available port number to facilitate connection hijacking or IP spoofing attacks. By anticipating the port used for a specific service, an attacker can inject malicious packets or intercept communication between two legitimate endpoints. This issue is characteristic of early TCP/IP stack implementations in various operating systems. Mitigation typically involves upgrading the operating system kernel to a version that implements ephemeral port randomization.

## Affected products

- Freebsd
- Linux Kernel
- Microsoft Windows Nt
- Netbsd

## Timeline

- 1997-07-01: disclosed

## References

- [https://www.cve.org/CVERecord?id=CVE-1999-0074](https://www.cve.org/CVERecord?id=CVE-1999-0074)

## Related threats

- [Linux IOMMU page table logic error in arm_lpae_split_blk_unmap](https://junglewise.ai/threats/cve-2026-56934-in-arm-lpae-split-blk-unmap-of-drivers-iommu-io-pgtable-arm)
- [Linux kernel null pointer dereference in TCP established lookup](https://junglewise.ai/threats/cve-2026-99288-in-the-linux-kernel-the-following-vulnerability-has-been-resolved)
- [Linux kernel xen-netback race condition in XenBus disconnect](https://junglewise.ai/threats/cve-2026-99286-in-the-linux-kernel-the-following-vulnerability-has-been-resolved)
- [Linux kernel shared-frag flag loss in skb_zerocopy](https://junglewise.ai/threats/cve-2026-99284-in-the-linux-kernel-the-following-vulnerability-has-been-resolved)
- [Linux kernel netfilter conntrack TCP RST timeout handling](https://junglewise.ai/threats/cve-2026-99283-in-the-linux-kernel-the-following-vulnerability-has-been-resolved)