Cyber Resilience

CVE-2026-33526

Memory Safety in Squid-Cache Squid ≤ 7.5

Memory Safety
Published
26 March 2026
Modified
15 July 2026
Patch / advisory
View advisory
CVSS Score v4 9.2
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS Score 0.089 95th percentile
Risk Priority 54 floored blend · peak EPSS

Summary

CVE-2026-33526 is a critical-severity Use After Free (CWE-416) vulnerability in Squid-Cache Squid. Its CVSS base score is 9.2 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 5% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

Squid, a caching proxy for the Web, is affected by a heap Use-After-Free vulnerability (CWE-416 and CWE-826) in versions prior to 7.5 when processing ICP traffic. The flaw produces a reliable and repeatable denial of service against the Squid service and is present only in deployments that explicitly configure a non-zero icp_port value. The CVSS 4.0 base score of 9.2 reflects network attackability with high impact on availability.

A remote attacker can trigger the condition by sending crafted ICP messages, resulting in service disruption. The attack succeeds regardless of icp_access rules that would otherwise deny ICP queries, so those controls provide no mitigation.

The Squid 7.5 release contains a patch for the issue. Public references include the fixing commit, the GitHub security advisory GHSA-hpfx-h48q-gvwg, and the oss-security mailing list announcement from March 2026. The associated EPSS values remain low with only a modest peak of 0.0229.

EU & UK References

Vulnerability Data

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…

more

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.

CWE(s)
CWE-416CWE-826CWE-825

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-32748Same product: Squid-Cache Squid
CVE-2023-49288Same product: Squid-Cache Squid
CVE-2026-53085Shared CWE-416, CWE-825
CVE-2026-31703Shared CWE-416, CWE-825
CVE-2026-12293Shared CWE-416, CWE-825
CVE-2026-6754Shared CWE-416, CWE-825
CVE-2026-45972Shared CWE-416, CWE-825
CVE-2024-23310Shared CWE-416, CWE-825
CVE-2026-52924Shared CWE-416, CWE-825
CVE-2026-4691Shared CWE-416, CWE-825

Affected Assets

squid-cache
squid
≤ 7.5

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 3 hardening rules · 3 OS baselines
Validate
Prove the fix (OWASP ASVS)
  • V1.4.3

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation can discover use-after-free bugs through dynamic analysis or fuzzing.

SA-8 Security and Privacy Engineering Principles partial match

Engineering principles can require memory-safe constructs or languages that structurally avoid introducing use-after-free.

SC-39 Process Isolation partial match

Process isolation confines the blast radius of use-after-free memory corruption to a single execution domain.

SI-16 Memory Protection partial match

Memory protection controls limit exploitation impact by blocking unauthorized code execution from dangling pointers.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly incorporate memory-safety tooling and reviews that prevent most use-after-free defects.

ID.AM-08 partial match
prevents

Lifecycle management includes secure development and maintenance phases that reduce memory-safety defects.

ID.RA-01 partial match
prevents

Vulnerability identification processes can discover use-after-free issues via scanning or analysis but do not prevent their introduction.

PR.PS-02 partial match
prevents

Routine patching removes known use-after-free instances after they have been introduced in released software.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development can detect use-after-free bugs before release.

A.8.25 Secure development life cycle partial match
prevents

Secure SDLC mandates memory-safety practices that reduce use-after-free defects.

A.8.26 Application security requirements partial match
prevents

Application security requirements can specify memory-management rules that mitigate use-after-free.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles include memory-safety design choices that limit use-after-free exposure.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly prescribe avoidance of use-after-free patterns.

A.8.32 Change management partial match
prevents

Change-management processes help ensure memory-safety fixes are deployed consistently.

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).

Oracle Linux 8 (1 rule)
  • V-248592 OL 8 must clear memory when it is freed to prevent use-after-free attacks. prevents CWE-416
RHEL 8 (1 rule)
  • V-230279 RHEL 8 must clear memory when it is freed to prevent use-after-free attacks. prevents CWE-416
RHEL 9 (1 rule)
  • V-257794 RHEL 9 must clear memory when it is freed to prevent use-after-free attacks. prevents CWE-416

References