BlackTreeCVE Intelligence
← Back to the CVE catalogue
Full vulnerability report · 2026
CVE-2026-33526High confidence

Squid vulnerable to Denial of Service in ICP Request handling

squid-cache · squid

Official source article: GitHub GHSA-HPFX-H48Q-GVWG ↗. Check the applicable product and release in the original source.

9.2CriticalCVSS 4.0
Recommended action
Within 72 hours

Critical technical impact with a remotely reachable, unauthenticated path; no CISA KEV confirmation is currently recorded.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityCriticalOperational priority:Critical, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 12.80% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs squid-cache squid and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Distribution package intelligence

Release-specific package status

Debian, ubuntu findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

5 package states
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Debian trixietrixie · sourcesquidVendor fix publishedDebian records a fixed source-package version for this release.6.13-2+deb13u2Debian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourcesquidVendor fix publishedDebian records a fixed source-package version for this release.5.7-2+deb12u6Debian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourcesquidVendor fix publishedDebian records a fixed source-package version for this release.7.5-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourcesquidVendor fix publishedDebian records a fixed source-package version for this release.7.5-1Debian Security Tracker ↗Source updated 5 Oct 2026
Ubuntu 24.04 LTSnoble · standard archivesquidVendor fix publishedCanonical reports that a fixed source package version has been published. Repository candidate availability is not checked by BlackTree.6.14-0ubuntu0.24.04.2Canonical Ubuntu Security ↗Source updated 5 Oct 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
CVE-2026-33526 · CSAF 2.0 · revision 7 · interimSUSE Product Security TeamCVE-2026-33526
49 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • squid as component of SUSE Linux Enterprise High Performance Computing 12 SP2
  • squid as component of SUSE Linux Enterprise High Performance Computing 12 SP4
  • squid as component of SUSE Linux Enterprise High Performance Computing 12 SP5
  • squid as component of SUSE Linux Enterprise High Performance Computing 15 SP1
  • squid as component of SUSE Linux Enterprise High Performance Computing 15 SP2
  • squid as component of SUSE Linux Enterprise High Performance Computing 15 SP3
  • squid as component of SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS
  • squid as component of SUSE Linux Enterprise High Performance Computing 15 SP4
  • squid as component of SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS
  • squid as component of SUSE Linux Enterprise High Performance Computing 15 SP5
  • squid as component of SUSE Linux Enterprise Module for Server Applications 15 SP7
  • squid as component of SUSE Linux Enterprise Server 12 SP2-LTSS
Summary
Squid is a caching proxy for the Web. Prior to version 7.5, due to heap Use-After-Free, Squid is vulnerable to Denial of Service when handling ICP traffic. This problem allows a remote attacker to perform a reliable and repeatable Denial of Service attack against the Squid service using ICP protocol. This attack is limited to Squid deployments that explicitly enable ICP support (i.e. configure non-zero `icp_port`). This problem _cannot_ be mitigated by denying ICP queries using `icp_access` rules. Version 7.5 contains a patch.
Remediation
To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-16068

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 72 hours

Critical technical impact with a remotely reachable, unauthenticated path; no CISA KEV confirmation is currently recorded.

Patch available
01

What, why and how

Squid is a caching proxy for the Web. Prior to version 7.5, due to heap Use-After-Free, Squid is vulnerable to Denial of Service when handling ICP traffic. This problem allows a remote attacker to perform a reliable and repeatable Denial of Service attack against the Squid service using ICP protocol. This attack is limited to Squid deployments that explicitly enable ICP support (i.e. configure non-zero `icp_port`). This problem _cannot_ be mitigated by denying ICP queries using `icp_access` rules. Version 7.5 contains a patch.

What

Squid is a caching proxy for the Web. Prior to version 7.5, due to heap Use-After-Free, Squid is vulnerable to Denial of Service when handling ICP traffic. This problem allows a remote attacker to perform a reliable and repeatable Denial of Service attack against the Squid service using ICP protocol. This attack is limited to Squid deployments that explicitly enable ICP support (i.e. configure non-zero `icp_port`). This problem _cannot_ be mitigated by denying ICP queries using `icp_access` rules. Version 7.5 contains a patch.

Why

The program can continue using memory after it has been released, producing unsafe and attacker-influenceable behaviour.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

What

Squid is a caching proxy for the Web. Prior to version 7.5, due to heap Use-After-Free, Squid is vulnerable to Denial of Service when handling ICP traffic. This problem allows a remote attacker to perform a reliable and repeatable Denial of Service attack against the Squid service using ICP protocol. This attack is limited to Squid deployments that explicitly enable ICP support (i.e. configure non-zero `icp_port`). This problem _cannot_ be mitigated by denying ICP queries using `icp_access` rules. Version 7.5 contains a patch.

Why

The program can continue using memory after it has been released, producing unsafe and attacker-influenceable behaviour.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Use After Free → disrupt the affected service
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Not a CVSS 4.0 base metric
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-416 ↗

CWE-416: Use After Free. The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

Common Vulnerability Scoring System 4.0: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.ATNoneAttack requirements: No additional deployment or execution condition is required.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.VCNoneVulnerable-system confidentiality: No direct loss is represented by this metric.VINoneVulnerable-system integrity: No direct loss is represented by this metric.VAHighVulnerable-system availability: A successful attack can cause a major loss.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SAHighSubsequent-system availability: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedDenial of serviceCWE-416
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

BSI · German · WID-SEC-2026-0854Squid: Mehrere Schwachstellen ermöglichen Denial of Service

Ein entfernter, anonymer Angreifer kann mehrere Schwachstellen in Squid ausnutzen, um einen Denial of Service Angriff durchzuführen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20260401Security Bulletin 01 Apr 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 01 Apr 2026, published on 1 April 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0376Multiples vulnérabilités dans les produits Microsoft

ulletin de sécurité Microsoft CVE-2026-23397 du 27 mars 2026 Bulletin de sécurité Microsoft CVE-2026-23398 du 27 mars 2026 Bulletin de sécurité Microsoft CVE-2026-27651 du 27 mars 2026 Bulletin de sécurité Microsoft CVE-2026-27654 du 27 mars 2026 Bulletin de sécurité Microsoft CVE-2026-27784 du 27 mars 2026 Bulletin de sécurité Microsoft CVE-2026-28753 du 27 mars 2026 Bulletin de sécurité Microsoft CVE-2026-28755 du 27 mars 2026 Bulletin de sécurité Microsoft CVE-2026-32647 du 27 mars 2026 Bulletin de sécurité Microsoft CVE-2026-32748 du 27 mars 2026 Bulletin de sécurité Microsoft CVE-2026-33515 du 27 mars 2026 Bulletin de sécurité Microsoft CVE-2026-33526 du 27 mars 2026 Bulletin de sécurité Microsoft CVE-2026-4645 du 27 mars 2026 Bulletin de sécurité Microsoft CVE-2026-33343 du 28 mars 2026 Bulletin de sécurité Microsoft CVE-2026-33413 du 28 mars 2026 Une gestion de version détaillée se trouve à la fin de ce document. Risque Non spécifié par l'éditeur Systèmes affectés azl3 etcd 3.5.21-1 versions antérieures à 3.5.28-1 azl3 glibc 2.38-18 versions antérieures à 2.38-19 azl3 kernel 6.6.126.1-1 versions antérieures à 6.6.130.1-1 azl3 libsoup 3.4.4-12 versions antérieures à 3.4.4-14 azl3 ncurses 6.4-2 versions antérieures à 6.4-3 azl3 nginx 1.28.2-1 versions antérieures à 1.28.3-1 azl3 python-py

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0350Multiples vulnérabilités dans Squid

De multiples vulnérabilités ont été découvertes dans Squid. Elles permettent à un attaquant de provoquer un déni de service à distance et une atteinte à la confidentialité des données.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-009487Squid-cache.orgのSquidにおける複数の脆弱性

SquidはWeb用のキャッシュプロキシです。バージョン7.5より前のバージョンでは、ヒープのUse-After-FreeによりICPトラフィック処理時にDenial of Service（サービス拒否）攻撃を受けやすい脆弱性が存在します。この問題により、リモートの攻撃者がICPプロトコルを利用してSquidサービスに対し、信頼性が高く再現可能なDenial of Service攻撃を実行できます。この攻撃は、ICPサポートを明示的に有効にしている（すなわち非ゼロの`icp_port`を設定している）Squidの導入環境に限定されます。この問題は`icp_access`ルールによるICPクエリの拒否では軽減できません。バージョン7.5にはこの問題を修正するパッチが含まれています。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
Fixed
RHSA-2026:8880: Red Hat Enterprise Linux Server (v. 7 ELS)
Action
To install this SUSE Security Update use the SUSE recommended installation methods like YaST online_update or "zypper patch".
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 26 Mar 2026 · Last source change 15 Jul 2026, 01:06 UTC · CWE-416 · Use After Free

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-16068
Product sourceVendor CSAF · SUSE Product Security Team
Remediation sourceVendor CSAF · SUSE Product Security Team
CWE sourceCNA
NVD statusNVD modified after enrichment

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗

No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.

Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-16068↗Vendor CSAF · SUSE Product Security Team↗CVE authority or vendor reference · GitHub GHSA-HPFX-H48Q-GVWG↗Patch or update reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-33526 · cve.blacktree.nl