NVD / CVE Program· CNA GitHub_M

CVE-2023-49288: Denial of Service in HTTP Collapsed Forwarding in Squid

Noroxi assessment

Priority: Monitor (action score 31/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 4.7% (FIRST EPSS); higher than 91.9% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to CISA the attack is automatable: targets can be found by mass scanning.
Fixed version: squid (Alpine:v3.19) 6.1-r0; squid (Debian:13) 6.1-1; squid (openSUSE:Tumbleweed) 6.6-2.1.

Low priority for now. Upgrade to squid (Alpine:v3.19) 6.1-r0; squid (Debian:13) 6.1-1; squid (openSUSE:Tumbleweed) 6.6-2.1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Squid is a caching proxy for the Web supporting HTTP, HTTPS, FTP, and more. Affected versions of squid are subject to a a Use-After-Free bug which can lead to a Denial of Service attack via collapsed forwarding. All versions of Squid from 3.5 up to and including 5.9 configured with "collapsed_forwarding on" are vulnerable. Configurations with "collapsed_forwarding off" or without a "collapsed_forwarding" directive are not vulnerable. This bug is fixed by Squid version 6.0.1. Users are advised to upgrade. Users unable to upgrade should remove all collapsed_forwarding lines from their squid.conf.

HighCVSS 7.5 · v3.1—No exploit Fix available

Published: Dec 4, 2023
Updated: Jun 17, 2026
EPSS: 4.7% · 91th percentile
CWE: CWE-416

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 30 / 40 · 7.5 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 1 / 30 · 4.7%

CISA SSVC decision

Exploitation: none
Automatable: yes
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: 7.5
CNA · GitHub_M: 8.6; 1.1 point gap

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
squid-cache	squid	cpe:2.3:a:squid-cache:squid

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

squid-cache squid3.5 and later · up to 5.9 inclusive

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

squid-cache squid
- >= 3.5, < 6.0.1affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Alpine:v3.19	squid	from 3.5 · before 6.1-r0	6.1-r0
Debian:12	squid	from 0	—
Debian:13	squid	before 6.1-1	6.1-1
openSUSE:Tumbleweed	squid	before 6.6-2.1	6.6-2.1
Red Hat:enterprise_linux:8::appstream	libecap	before 0:1.0.1-2.module+el8.9.0+19703+a1da7223	0:1.0.1-2.module+el8.9.0+19703+a1da7223
Red Hat:enterprise_linux:8::appstream	libecap-debuginfo	before 0:1.0.1-2.module+el8.9.0+19703+a1da7223	0:1.0.1-2.module+el8.9.0+19703+a1da7223
Red Hat:enterprise_linux:8::appstream	libecap-debugsource	before 0:1.0.1-2.module+el8.9.0+19703+a1da7223	0:1.0.1-2.module+el8.9.0+19703+a1da7223
Red Hat:enterprise_linux:8::appstream	libecap-devel	before 0:1.0.1-2.module+el8.9.0+19703+a1da7223	0:1.0.1-2.module+el8.9.0+19703+a1da7223
Red Hat:enterprise_linux:8::appstream	squid	before 7:4.15-7.module+el8.9.0+20806+014d88aa.3	7:4.15-7.module+el8.9.0+20806+014d88aa.3
Red Hat:enterprise_linux:8::appstream	squid-debuginfo	before 7:4.15-7.module+el8.9.0+20806+014d88aa.3	7:4.15-7.module+el8.9.0+20806+014d88aa.3
Red Hat:enterprise_linux:8::appstream	squid-debugsource	before 7:4.15-7.module+el8.9.0+20806+014d88aa.3	7:4.15-7.module+el8.9.0+20806+014d88aa.3
Red Hat:enterprise_linux:9::appstream	squid	before 7:5.5-6.el9_3.2	7:5.5-6.el9_3.2
Red Hat:enterprise_linux:9::appstream	squid-debuginfo	before 7:5.5-6.el9_3.2	7:5.5-6.el9_3.2
Red Hat:enterprise_linux:9::appstream	squid-debugsource	before 7:5.5-6.el9_3.2	7:5.5-6.el9_3.2
SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS	squid	before 5.7-150400.3.41.1	5.7-150400.3.41.1

Same product

squid-cache: all records

Other highest-scoring records for the same primary product.

CVE-2024-25617Denial of Service in HTTP Header parser in squid proxy
56Plan
CVE-2023-49285Denial of Service in HTTP Message Processing in Squid
56Plan
CVE-2021-31806An issue was discovered in Squid before 4.15 and 5.x before 5.0.6.
55Plan

Published before and after this one in the same product

← EarlierCVE-2023-46728Nov 6, 2023 · SQUID-2021:8 Denial of Service in Gopher gateway
32Monitor
← EarlierCVE-2023-49286Dec 4, 2023 · Denial of Service in Helper Process management
33Monitor
Later →CVE-2023-50269Dec 14, 2023 · SQUID-2023:10 Denial of Service in HTTP Request parsing
47Plan

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
alpine:squid	6.1-r0 · Alpine:v3.19	Package registry (OSV)
debian:squid	6.1-1 · Debian:13	Package registry (OSV)
opensuse:squid	6.6-2.1 · openSUSE:Tumbleweed	Package registry (OSV)
red hat:libecap	0:1.0.1-2.module+el8.9.0+19703+a1da7223 · Red Hat:enterprise_linux:8::appstream	Package registry (OSV)
red hat:libecap-debuginfo	0:1.0.1-2.module+el8.9.0+19703+a1da7223 · Red Hat:enterprise_linux:8::appstream	Package registry (OSV)
red hat:libecap-debugsource	0:1.0.1-2.module+el8.9.0+19703+a1da7223 · Red Hat:enterprise_linux:8::appstream	Package registry (OSV)
red hat:libecap-devel	0:1.0.1-2.module+el8.9.0+19703+a1da7223 · Red Hat:enterprise_linux:8::appstream	Package registry (OSV)
red hat:squid	7:5.5-6.el9_3.2 · Red Hat:enterprise_linux:9::appstream	Package registry (OSV)
red hat:squid-debuginfo	7:5.5-6.el9_3.2 · Red Hat:enterprise_linux:9::appstream	Package registry (OSV)
red hat:squid-debugsource	7:5.5-6.el9_3.2 · Red Hat:enterprise_linux:9::appstream	Package registry (OSV)
suse:squid	5.7-150400.3.41.1 · SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOS	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: none
Integrity: none
Availability: high · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: None
Integrity impact: None
Availability impact: High

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1free(dev->buf);
2/* ... another thread is still running ... */
3process(dev->buf);

Fixed

1lock(&dev->lock);
2free(dev->buf);
3dev->buf = NULL;
4unlock(&dev->lock);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

Fix✗ → ✓Sep 28, 2026, 10:45 PM UTC

For records you follow, these changes also arrive as notifications. →

References

github.com/squid-cache/squid/security/advisories/GHSA-rj5h-46j6-q2g5

Show all references (3 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records