Bug 1139967 (CVE-2014-6270) - CVE-2014-6270 squid: off-by-one error in snmpHandleUdp() leading to a bss-based buffer overflow (SQUID-2014:3)
Summary: CVE-2014-6270 squid: off-by-one error in snmpHandleUdp() leading to a bss-bas...
Alias: CVE-2014-6270
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
Depends On: 1139968
Blocks: 1139969
TreeView+ depends on / blocked
Reported: 2014-09-10 05:48 UTC by Murray McAllister
Modified: 2021-06-15 15:04 UTC (History)
5 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2021-06-15 15:04:22 UTC

Attachments (Terms of Use)
Local copy of the proposed patch (632 bytes, patch)
2014-09-12 11:19 UTC, Tomas Hoger
no flags Details | Diff

Description Murray McAllister 2014-09-10 05:48:07 UTC
Sebastian Krahmer discovered an off-by-one error, leading to a heap-based buffer overflow flaw, in the way Squid handled UDP SNMP requests. An unauthenticated, remote attacker could possibly use this flaw to crash Squid or, potentially, execute arbitrary code.

As noted in Sebastian's original report, an SNMP port must be configured. The default configuration of Squid for Red Hat Enterprise Linux 6 and 7 does not include an snmp_port declaration (http://wiki.squid-cache.org/Features/Snmp).





Comment 1 Murray McAllister 2014-09-10 05:49:50 UTC
Created squid tracking bugs for this issue:

Affects: fedora-all [bug 1139968]

Comment 3 Tomas Hoger 2014-09-11 19:14:06 UTC
This actually is a BSS based overflow, not heap based as mentioned in the original report.  The actual impact of such overflow is build specific, the issue is unlikely to produce reliable crash of the program.

This flaw exists in the code that handles SNMP packets.  As noted in comment 0, Squid's SNMP agent is not enabled by default.  Hence squid packages in Red Hat Enterprise Linux and Fedora are not affected in their default configuration.  SNMP agent is can be enabled by specifying non-zero value for the snmp_port configuration directive.

There are multiple options to mitigate this issue:

- Do not enable SNMP support if it's not needed.  Ensure squid configuration either does not include snmp_port directive, or sets its value to 0.

- Restrict access to SNMP port only to trusted networks or hosts.  The snmp_incoming_address configuration directive can be used to bind SNMP agent to a specific IP / network interface (e.g. when using multi-homed server with a connection to trusted management network), or firewall configuration can be used to block access from untrusted sources.  Note that as UDP is used, firewall restrictions may be bypassed using packets with spoofed source address sent from at least the local network.

- Filter packets that are large enough to trigger the overflow - i.e. packets that have at least 4096 bytes.  Iptables rule similar to the below one can be used to reject IPv4 packets of the given size (value used in the rule takes IP and UDP header size into account).

# iptables -A INPUT -p udp --dport 3401 -m length --length 4124: -j REJECT

Comment 5 Tomas Hoger 2014-09-12 08:10:46 UTC
Lowering impact rating as this is functionality disabled by default, not needed for normal proxy operation, not needed to be exposed to untrusted users, overflow is too limited and difficult to exploit, and mitigation is available.

Comment 6 Tomas Hoger 2014-09-12 08:11:59 UTC

This issue affects the versions of squid as shipped with Red Hat Enterprise Linux 5, 6, and 7. Red Hat Product Security has rated this issue as having Moderate security impact. A future update may address this issue. For additional information, refer to the Issue Severity Classification: https://access.redhat.com/security/updates/classification/.

Comment 7 Tomas Hoger 2014-09-12 11:19:37 UTC
Created attachment 936923 [details]
Local copy of the proposed patch


Comment 9 Murray McAllister 2014-10-01 06:17:29 UTC
External References:


Comment 10 Fedora Update System 2014-10-14 04:39:51 UTC
squid-3.4.7-2.fc21 has been pushed to the Fedora 21 stable repository.  If problems still persist, please make note of it in this bug report.

Comment 11 Fedora Update System 2014-10-14 04:40:28 UTC
squid-3.3.13-2.fc19 has been pushed to the Fedora 19 stable repository.  If problems still persist, please make note of it in this bug report.

Comment 12 Fedora Update System 2014-10-14 04:46:07 UTC
squid-3.3.13-2.fc20 has been pushed to the Fedora 20 stable repository.  If problems still persist, please make note of it in this bug report.

Comment 14 Alexander Buchner 2016-05-06 10:04:30 UTC
Are there any plans to fix this bug in RHEL 6?

Comment 15 Product Security DevOps Team 2021-06-15 15:04:22 UTC
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s):


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