dbcve.org
ScreenosOperating system · Juniper

CVE-2015-7756

MEDIUM · 5.0 CVSS v2.0 Published 2015-12-19
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
59/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The encryption implementation in Juniper ScreenOS 6.2.0r15 through 6.2.0r18, 6.3.0r12 before 6.3.0r12b, 6.3.0r13 before 6.3.0r13b, 6.3.0r14 before 6.3.0r14b, 6.3.0r15 before 6.3.0r15b, 6.3.0r16 before 6.3.0r16b, 6.3.0r17 before 6.3.0r17b, 6.3.0r18 before 6.3.0r18b, 6.3.0r19 before 6.3.0r19b, and 6.3.0r20 before 6.3.0r21 makes it easier for remote attackers to discover the plaintext content of VPN sessions by sniffing the network for ciphertext data and conducting an unspecified decryption attack.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Juniper ScreenOS VPN devices running versions 6.2.0r15-r18 and 6.3.0r12-r20 contain a weakened encryption implementation that allows remote attackers to recover plaintext VPN session content by sniffing network traffic and conducting a decryption attack against the ciphertext.

MitigationUpgrade ScreenOS to versions 6.2.0r19+, 6.3.0r12b+, 6.3.0r13b+, 6.3.0r14b+, 6.3.0r15b+, 6.3.0r16b+, 6.3.0r17b+, 6.3.0r18b+, 6.3.0r19b+, or 6.3.0r21+ as specified in Juniper advisory. If immediate patching is not feasible, implement enhanced network traffic monitoring for anomalous VPN patterns.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
ScreenosOperating system
Affected:= 6.2.0r15= 6.2.0r16= 6.2.0r17= 6.2.0r18= 6.3.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Authentication
None
Confidentiality
Partial
Integrity
None
Availability
None

AV:N/AC:L/Au:N/C:P/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify device OS and model
    Run 'get system' or 'show system information' command on the Juniper device to confirm it is running ScreenOS and note the hardware model
    Affected if Device is not running ScreenOS (not affected)
  2. Check ScreenOS version
    Run 'get system' or 'show version' command to retrieve the exact ScreenOS firmware version number
    Affected if Version is 6.2.0r15, 6.2.0r16, 6.2.0r17, 6.2.0r18, or any 6.3.0 release from r12 through r20, or exactly 6.3.0 (vulnerable)
  3. Confirm VPN feature is configured
    Run 'get vpn' or 'show vpn' command to list active VPN tunnels and their status on the device
    Affected if No VPN tunnels are configured (the vulnerability only affects active VPN sessions)
  4. Inspect VPN encryption configuration
    Run 'get vpn <tunnel_name>' or 'show vpn configuration' to review the encryption algorithm and key exchange settings for each VPN tunnel
    Affected if VPN tunnels are using default or weak encryption algorithms (vulnerable to plaintext recovery)
  5. Review VPN traffic on the network
    Capture and analyze VPN-encrypted traffic using network sniffing tools to verify if traffic matches expected cipher strength
    Affected if Sniffed VPN traffic shows predictable patterns consistent with the weakened encryption (indicates active exploitation or vulnerability present)

Device is affected if it runs ScreenOS versions 6.2.0r15 through 6.2.0r18, or 6.3.0r12 through 6.3.0r20 (or exactly 6.3.0) AND has active VPN tunnels configured using the weakened encryption implementation.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade ScreenOS to versions 6.2.0r19+, 6.3.0r12b+, 6.3.0r13b+, 6.3.0r14b+, 6.3.0r15b+, 6.3.0r16b+, 6.3.0r17b+, 6.3.0r18b+, 6.3.0r19b+, or 6.3.0r21+ as specified in Juniper advisory. If immediate patching is not feasible, implement enhanced network traffic monitoring for anomalous VPN patterns.

Fix this in Screenos Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,440
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2015-7756 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data