CVE-2023-0836

An information leak vulnerability was discovered in HAProxy 2.1, 2.2 before 2.2.27, 2.3, 2.4 before 2.4.21, 2.5 before 2.5.11, 2.6 before 2.6.8, 2.7 before 2.7.1. There are 5 bytes left uninitialized in the connection buffer when encoding the FCGI_BEGIN_REQUEST record. Sensitive data may be disclosed to configured FastCGI backends in an unexpected way.

Published: 2023-03-29 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-0836 is rated Moderate Risk (53.6/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.20%). EPSS rose +1.20% over the last day, indicating growing attacker interest. Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2023-0836

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.00% 1.20% +1.20%
2 2025-03-17 0.16% 0.00% -0.15%
3 2024-04-30 — 0.16% —

Full EPSS history (5 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-0836

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/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]
7.5 3.1 HIGH
CVSS:3.1/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 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2023-0836

OS Trackers for CVE-2023-0836

vendor priority summary link
debian not yet assigned CVE-2023-0836 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-2023-0836
redhat medium — https://access.redhat.com/security/cve/CVE-2023-0836
suse medium CVE-2023-0836 severity moderate: SUSE including 2 source package names (haproxy, haproxy-2.4.22-1.el9), 16 product×package rows across 16 product lines (HPE Helion OpenStack 8, SUSE Liberty Linux 9, … (16 product lines)): Known Not Affected 15, Fixed 1. https://www.suse.com/security/cve/CVE-2023-0836/
ubuntu medium CVE-2023-0836 medium priority: Ubuntu including 1 source packages (haproxy), 8 status rows across 8 suites (bionic, focal, jammy, kinetic, lunar, trusty, upstream, xenial): not-affected 4, released 3, ignored 1. https://ubuntu.com/security/CVE-2023-0836

Affected software / configurations for CVE-2023-0836

Vendor Product Version Raw CPE
haproxy haproxy >= 2.2.0, < 2.2.27 cpe:2.3:a:haproxy:haproxy:*:*:*:*:*:*:*:*
haproxy haproxy >= 2.4.0, <= 2.4.21 cpe:2.3:a:haproxy:haproxy:*:*:*:*:*:*:*:*
haproxy haproxy >= 2.5.0, <= 2.5.11 cpe:2.3:a:haproxy:haproxy:*:*:*:*:*:*:*:*
haproxy haproxy >= 2.6.0, <= 2.6.8 cpe:2.3:a:haproxy:haproxy:*:*:*:*:*:*:*:*
haproxy haproxy 2.1.0 cpe:2.3:a:haproxy:haproxy:2.1.0:*:*:*:*:*:*:*
haproxy haproxy 2.3.0 cpe:2.3:a:haproxy:haproxy:2.3.0:*:*:*:*:*:*:*
haproxy haproxy 2.7.0 cpe:2.3:a:haproxy:haproxy:2.7.0:*:*:*:*:*:*:*

References for CVE-2023-0836

cvelogic Threat Intelligence