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Fencer Intel
high 7.5

CVE-2012-2663 json

extensions/libxt_tcp.c in iptables through 1.4.21 does not match TCP SYN+FIN packets in --syn rules, which might allow remote attackers to…

published 2014-02-15 12 y ago modified 2026-06-16 4 mo ago also EUVD-2012-2646

cvss
7.5
version 2.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.7%
EPSS 2.7% chance of exploitation in 30 days, percentile 86%
public exploits
0
none known

Summary

extensions/libxt_tcp.c in iptables through 1.4.21 does not match TCP SYN+FIN packets in --syn rules, which might allow remote attackers to bypass intended firewall restrictions via crafted packets. NOTE: the CVE-2012-6638 fix makes this issue less relevant.

Patch / fix

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2012-2663 updated cvss 6.4

iptables: --syn flag bypass

  • Red Hat Enterprise Linux 5 iptables Red Hat Enterprise Linux 6 iptables, iptables-ipv6
    affected: workaround, no fix available “Instead of --syn use --tcp-flags SYN,RST,ACK SYN in your rulesets in case you want to also match packets with both SYN+FIN flags set.”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.74% chance of exploitation in the next 30 days, higher than 86% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.