CVE-2018-20102 [High] | Out-of-bounds Read in Haproxy

An out-of-bounds read in dns_validate_dns_response in dns.c was discovered in HAProxy through 1.8.14. Due to a missing check when validating DNS responses, remote attackers might be able read the 16 bytes corresponding to an AAAA record from the non-initialized part of the buffer, possibly accessing anything that was left on the stack, or even past the end of the 8193-byte buffer, depending on the value of accepted_payload_size.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.02%	4.35%	+4.33%
2	2025-03-30	0.07%	0.02%	-0.05%
3	2025-03-29	—	0.07%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.02%

4.35%

+4.33%

2025-03-30

0.07%

0.02%

-0.05%

2025-03-29

—

0.07%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.5	3.0	HIGH	`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:N) Service keeps running; no real outage angle.	3.9	3.6	[email protected]
5.0	2.0	MEDIUM	`AV:N/AC:L/Au:N/C:P/I:N/A:N` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:N) No authentication is required. Confidentiality impact (C:P) Partial confidentiality impact. Integrity impact (I:N) No integrity impact. Availability impact (A:N) No availability impact.	10.0	2.9	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

7.5

3.0

HIGH

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N Click to expand

Attack vector (AV:N): Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H): Serious risk that confidential data gets exposed in a big way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:N): Service keeps running; no real outage angle.

3.9

3.6

[email protected]

5.0

2.0

MEDIUM

AV:N/AC:L/Au:N/C:P/I:N/A:N Click to expand

Access vector (AV:N): Can be exploited remotely over network reachability.
Access complexity (AC:L): Exploitation conditions are straightforward and predictable.
Authentication (AU:N): No authentication is required.
Confidentiality impact (C:P): Partial confidentiality impact.
Integrity impact (I:N): No integrity impact.
Availability impact (A:N): No availability impact.

10.0

2.9

[email protected]

OS Trackers for CVE-2018-20102

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2018-20102 not yet assigned priority: Debian including 1 source packages (haproxy), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5.	https://security-tracker.debian.org/tracker/CVE-2018-20102
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2018-20102
`suse`	medium	CVE-2018-20102 severity moderate: SUSE including 8 source package names (haproxy, haproxy-1.8.15~git0.6b6a350a-3.6.2, …), 19 product×package rows across 19 product lines (HPE Helion OpenStack 8, SUSE Linux Enterprise High Availability Extension 12, … (19 product lines)): Known Not Affected 12, Fixed 7.	https://www.suse.com/security/cve/CVE-2018-20102/
`ubuntu`	medium	CVE-2018-20102 medium priority: Ubuntu including 1 source packages (haproxy), 5 status rows across 5 suites (bionic, cosmic, trusty, upstream, xenial): released 4, DNE 1.	https://ubuntu.com/security/CVE-2018-20102

Affected software / configurations for CVE-2018-20102

Vendor	Product	Version	Raw CPE
haproxy	haproxy	<= 1.8.14	cpe:2.3:a:haproxy:haproxy::::::::
canonical	ubuntu_linux	16.04	cpe:2.3:o:canonical:ubuntu_linux:16.04::::lts:::
canonical	ubuntu_linux	18.04	cpe:2.3:o:canonical:ubuntu_linux:18.04::::lts:::
canonical	ubuntu_linux	18.10	cpe:2.3:o:canonical:ubuntu_linux:18.10:::::::*
redhat	openshift_container_platform	3.11	cpe:2.3:a:redhat:openshift_container_platform:3.11:::::::*

References for CVE-2018-20102

URL	Tags
http://git.haproxy.org/?p=haproxy.git%3Ba=commit%3Bh=efbbdf72992cd20458259962346044cafd9331c0
http://www.securityfocus.com/bid/106223	Third Party Advisory VDB Entry
https://access.redhat.com/errata/RHBA-2019:0326	Third Party Advisory
https://access.redhat.com/errata/RHBA-2019:0327	Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:1436
https://lists.debian.org/debian-lts-announce/2022/05/msg00045.html
https://usn.ubuntu.com/3858-1/	Third Party Advisory

URL

CVE-2018-20102

Exploit prediction scoring system (EPSS) score for CVE-2018-20102

Common vulnerability scoring system (CVSS) metrics for CVE-2018-20102

Weakness enumeration for CVE-2018-20102

OS Trackers for CVE-2018-20102

Affected software / configurations for CVE-2018-20102

References for CVE-2018-20102