CVE-2016-6594: Blue Coat Advanced Secure Gateway 6.6, CacheFlow 3.4, ProxySG 6.5 and 6.6 allows remote attackers to bypass bl

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HIGH 7.5REMOTEDOWNGRADEDOWNGRADEDOWNGRADE

CVE-2016-6594 is a high-severity flaw (CVSS 7.5) affecting advanced secure gateway, cacheflow, proxysg. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Blue Coat Advanced Secure Gateway 6.6, CacheFlow 3.4, ProxySG 6.5 and 6.6 allows remote attackers to bypass blocked requests, user authentication, and payload scanning.

Why this priority

High severity
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.3% (top 30%)
CISA exploited list	No
Weakness	CWE-254
Published	2017-06-08
Last modified	2026-06-17

Publisher (CNA): Symantec Corporation · Vendor: bluecoat

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2017-06-08 20:29 UTCPublished CVE record published
2026-06-17 00:51 UTCUpdated Record last modified

bluecoat advanced secure gateway DOWNGRADE

Affected: 6.6

Fixed in: no fixed release known

Safe to downgrade to: a release before 6.6

1. Check installed version

apt-cache policy advanced-secure-gateway || rpm -q advanced-secure-gateway || advanced-secure-gateway --version

2. No fixed release: DOWNGRADE to a release before 6.6 (Debian / Ubuntu)

apt-cache madison advanced-secure-gateway sudo apt install advanced-secure-gateway=<VERSION_BEFORE_6.6> sudo apt-mark hold advanced-secure-gateway

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list advanced-secure-gateway sudo dnf downgrade advanced-secure-gateway-<VERSION_BEFORE_6.6> sudo dnf versionlock add advanced-secure-gateway

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

bluecoat cacheflow DOWNGRADE

Affected: 3.4

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.4

1. Check installed version

apt-cache policy cacheflow || rpm -q cacheflow || cacheflow --version

2. No fixed release: DOWNGRADE to a release before 3.4 (Debian / Ubuntu)

apt-cache madison cacheflow sudo apt install cacheflow=<VERSION_BEFORE_3.4> sudo apt-mark hold cacheflow

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list cacheflow sudo dnf downgrade cacheflow-<VERSION_BEFORE_3.4> sudo dnf versionlock add cacheflow

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

bluecoat proxysg DOWNGRADE

Affected: 6.5 · 6.6

Fixed in: no fixed release known

Safe to downgrade to: a release before 6.5

1. Check installed version

apt-cache policy proxysg || rpm -q proxysg || proxysg --version

2. No fixed release: DOWNGRADE to a release before 6.5 (Debian / Ubuntu)

apt-cache madison proxysg sudo apt install proxysg=<VERSION_BEFORE_6.5> sudo apt-mark hold proxysg

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list proxysg sudo dnf downgrade proxysg-<VERSION_BEFORE_6.5> sudo dnf versionlock add proxysg

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2016-6594?

advanced secure gateway: downgrade or apply the listed mitigation; cacheflow: downgrade or apply the listed mitigation; proxysg: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2016-6594 being exploited?

CVE-2016-6594 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2016-6594 affect?

CVE-2016-6594 affects advanced secure gateway, cacheflow, proxysg. Severity is high (CVSS 7.5). Blue Coat Advanced Secure Gateway 6.6, CacheFlow 3.4, ProxySG 6.5 and 6.6 allows remote attackers to bypass blocked requests, user authentication, and payload scanning.

How urgent is CVE-2016-6594?

Priority 49/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2023-23955 HIGH 8.1 UPGRADE UPGRADE Advanced Secure Gateway and Content Analysis, prior to 7.3.13.1 / 3.1.6.0, may be susceptible to a Server-Side
CVE-2023-23954 MEDIUM 5.4 UPGRADE UPGRADE Advanced Secure Gateway and Content Analysis, prior to 7.3.13.1 / 3.1.6.0, may be susceptible to a Stored Cros
CVE-2023-23953 HIGH 7.8 UPGRADE UPGRADE Advanced Secure Gateway and Content Analysis, prior to 7.3.13.1 / 3.1.6.0, may be susceptible to an Elevation
CVE-2023-23952 CRITICAL 9.8 UPGRADE UPGRADE Advanced Secure Gateway and Content Analysis, prior to 7.3.13.1 / 3.1.6.0, may be susceptible to a Command Inj
CVE-2021-46825 CRITICAL 9.1 DOWNGRADE DOWNGRADE Symantec Advanced Secure Gateway (ASG) and ProxySG are susceptible to an HTTP desync vulnerability

References

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