Squid before 3.5.6 does not properly handle CONNECT method peer responses when configured with cache_peer, which allows remote attackers to
Noroxi assessment
Priority: Monitor (action score 33/100)
- 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: 20.8% (FIRST EPSS); higher than 97.5% of all records.
- Fixed version: squid (Debian:12) 4.1-1; squid3 (Debian:6.0) 3.1.6-1.2+squeeze5; squid3 (Debian:7) 3.1.20-2.2+deb7u3.
Low priority for now. Upgrade to squid (Debian:12) 4.1-1; squid3 (Debian:6.0) 3.1.6-1.2+squeeze5; squid3 (Debian:7) 3.1.20-2.2+deb7u3 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
Squid before 3.5.6 does not properly handle CONNECT method peer responses when configured with cache_peer, which allows remote attackers to bypass intended restrictions and gain access to a backend proxy via a CONNECT request.
- Published
- Sep 28, 2015
- Updated
- Jun 16, 2026
- EPSS
- 20.8% · 98th percentile
- CWE
- CWE-264
Report tools
Action score
33
Monitor
Low priority for now.
- CVSS
- 27 / 40 · 6.8 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 6 / 30 · 20.8%
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
If any of these changes, we'll tell you in the daily email digest.
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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.
We use this product, ask for helpAffected 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 |
|---|---|---|
| fedoraproject | fedora | cpe:2.3:o:fedoraproject:fedora |
| debian | debian linux | cpe:2.3:o:debian:debian_linux |
| 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.
- debian debian linux7.0
- debian debian linux8.0
- fedoraproject fedora22
- squid-cache squidup to 3.5.2 inclusive
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | squid | before 4.1-1 | 4.1-1 |
| Debian:6.0 | squid3 | before 3.1.6-1.2+squeeze5 | 3.1.6-1.2+squeeze5 |
| Debian:7 | squid3 | before 3.1.20-2.2+deb7u3 | 3.1.20-2.2+deb7u3 |
| Debian:8 | squid3 | before 3.4.8-6+deb8u1 | 3.4.8-6+deb8u1 |
| openSUSE:Tumbleweed | squid | before 3.5.22-1.1 | 3.5.22-1.1 |
| SUSE:Linux Enterprise Server 11 SP4 | squid3 | before 3.1.23-8.16.30.1 | 3.1.23-8.16.30.1 |
| SUSE:Linux Enterprise Server 12 SP1 | squid | before 3.3.14-20.2 | 3.3.14-20.2 |
Same product
fedoraproject: all recordsOther highest-scoring records for the same primary product.
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- CVE-2016-2173org.springframework.core.serializer.DefaultDeserializer in Spring AMQP before 1.5.5 allows remote attackers to execute arbitrary code.41Plan
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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 |
|---|---|---|
| debian:squid | 4.1-1 · Debian:12 | Package registry (OSV) |
| debian:squid3 | 3.1.6-1.2+squeeze5 · Debian:6.0 | Package registry (OSV) |
| opensuse:squid | 3.5.22-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| suse:squid | 3.3.14-20.2 · SUSE:Linux Enterprise Server 12 SP1 | Package registry (OSV) |
| suse:squid3 | 3.1.23-8.16.30.1 · SUSE:Linux Enterprise Server 11 SP4 | 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.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
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 researchersFinders, 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
If successful
- Confidentiality
- P · data can be read
- Integrity
- P · data or configuration can be modified
- Availability
- P · the service can be disrupted
- Attack complexity
- M
- Confidentiality impact
- P
- Integrity impact
- P
- Availability impact
- P
Weakness class (CWE)
CWE-264 · Permissions, Privileges, and Access ControlsCVSS vector
AV:N/AC:M/Au:N/C:P/I:P/A:P
nvd-primary
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✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (10 more)Show less
- lists.opensuse.org/opensuse-security-announce/2016-08/msg00010.html
- lists.opensuse.org/opensuse-security-announce/2016-08/msg00040.html
- lists.opensuse.org/opensuse-updates/2016-08/msg00069.html
- www.debian.org/security/2015/dsa-3327
- www.openwall.com/lists/oss-security/2015/07/06/8
- www.openwall.com/lists/oss-security/2015/07/09/12
- www.openwall.com/lists/oss-security/2015/07/10/2
- www.securityfocus.com/bid/75553
- www.securitytracker.com/id/1032873
- www.squid-cache.org/Advisories/SQUID-2015_2.txt
Vendor advisories and official records. Exploit/PoC links are deliberately left out.