Description
The ip_push_pending_frames function in Linux 2.4.x and 2.6.x before 2.6.16 increments the IP ID field when sending a RST after receiving unsolicited TCP SYN-ACK packets, which allows remote attackers to conduct an Idle Scan (nmap -sI) attack, which bypasses intended protections against such attacks.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 3.1 | kernel-source-2.4.27 | 2.4.27-10sarge3 | DSA-1097-1 |
| Debian 3.1 | kernel-source-2.6.8 | 2.6.8-16sarge3 | DSA-1103 |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 4 | kernel +8 | 2.6.9-42.EL | RHSA-2006:0575 |
| RHEL 3 | kernel +8 | 2.4.21-47.EL | RHSA-2006:0437 |
Advisories 4
- RHSA-2006:0575 Red Hat Security Advisory: Updated kernel packages available for Red Hat Enterprise Linux 4 Update 4 Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2006:0437 Red Hat Security Advisory: Updated kernel packages for Red Hat Enterprise Linux 3 Update 8 Red Hat Security Advisories (RHSA) · Jun 26, 2026
- DSA-1097-1 kernel-source-2.4.27 - several vulnerabilities Debian Security (DSA / DLA) · Mar 9, 2026
- DSA-1103 kernel-source-2.6.8 - several vulnerabilities Debian Security (DSA / DLA) · Mar 9, 2026
References
- RHSA-2006:0437 vendor-advisory
- ADV-2006-2554 vdb-entry
- http://www.kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.16.1
- 20060315 Re: Linux zero IP ID vulnerability? mailing-list
- USN-281-1 vendor-advisory
- 21136 third-party-advisory
- 19402 third-party-advisory
- 20060316 Re: Linux zero IP ID vulnerability? mailing-list
- 21983 third-party-advisory
- 17109 vdb-entry
- DSA-1097 vendor-advisory
- RHSA-2006:0575 vendor-advisory
- 20060314 Linux zero IP ID vulnerability? mailing-list
- SUSE-SA:2006:028 vendor-advisory
- 19955 third-party-advisory
- 20060323 Re: Linux zero IP ID vulnerability? mailing-list
- http://support.avaya.com/elmodocs2/security/ASA-2006-180.htm
- DSA-1103 vendor-advisory
- 21465 third-party-advisory
- oval:org.mitre.oval:def:10317 vdb-entry signature
- ADV-2006-1140 vdb-entry
- http://support.avaya.com/elmodocs2/security/ASA-2006-200.htm
- 20398 third-party-advisory
- 22417 third-party-advisory
- MDKSA-2006:086 vendor-advisory
- 20671 third-party-advisory
- 20157 third-party-advisory
- 20914 third-party-advisory