CVE-2023-5824 | Squid: dos against http and https

A flaw was found in Squid. The limits applied for validation of HTTP response headers are applied before caching. However, Squid may grow a cached HTTP response header beyond the configured maximum size, causing a stall or crash of the worker process when a large header is retrieved from the disk cache, resulting in a denial of service.

Published: 2023-11-03 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2023-5824 is rated High Risk (65.3/100): CVSS High severity, with high exploitation likelihood (EPSS 5.23%, 91th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. EPSS rose +3.35% over the last day, indicating growing attacker interest. High exploitation likelihood—assess exposure and prioritize 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-2023-5824

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 1.88% 5.23% +3.35%
2 2026-01-17 1.56% 1.88% +0.32%
3 2025-12-28 — 1.56% —

Full EPSS history (45 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2023-5824

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:N/I:N/A:H 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:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 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:N/I:N/A:H 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:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2023-5824

OS Trackers for CVE-2023-5824

vendor priority summary link
alpine — CVE-2023-5824: 1 source package rows (squid); 57 state rows across 7 repos (3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 0, open 57. https://security.alpinelinux.org/vuln/CVE-2023-5824
debian not yet assigned CVE-2023-5824 not yet assigned priority: Debian including 1 source packages (squid), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2023-5824
redhat high — https://access.redhat.com/security/cve/CVE-2023-5824
suse high CVE-2023-5824 severity important: SUSE including 5 source package names (squid, squid-5.5-6.el9_3.2, squid-6.10-150600.3.6.1, squid-6.12-160000.2.2, squid-6.4-1.1), 18 product×package rows across 17 product lines (SUSE Liberty Linux 9, SUSE Linux Enterprise Module for Server Applications 15 SP6, … (17 product lines)): Known Not Affected 14, Fixed 4. https://www.suse.com/security/cve/CVE-2023-5824/
ubuntu medium CVE-2023-5824 medium priority: Ubuntu including 2 source packages (squid, squid3), 24 status rows across 12 suites (bionic, focal, jammy, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 8, released 8, ignored 5, needed 2, needs-triage 1. https://ubuntu.com/security/CVE-2023-5824

Affected software / configurations for CVE-2023-5824

Vendor Product Version Raw CPE
squid-cache squid < 6.4 cpe:2.3:a:squid-cache:squid:*:*:*:*:*:*:*:*
redhat enterprise_linux 6.0 cpe:2.3:o:redhat:enterprise_linux:6.0:*:*:*:*:*:*:*
redhat enterprise_linux 7.0 cpe:2.3:o:redhat:enterprise_linux:7.0:*:*:*:*:*:*:*
redhat enterprise_linux 8.0 cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:*
redhat enterprise_linux 9.0 cpe:2.3:o:redhat:enterprise_linux:9.0:*:*:*:*:*:*:*

References for CVE-2023-5824

cvelogic Threat Intelligence