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Debian LinuxOperating system · Debian

CVE-2015-5291

MEDIUM · 6.8 CVSS v2.0 Published 2015-11-02
Fix available
A fix is available. Upgrade to 1.2.17 / 1.3.14 or later.
See remediation →
77/100
Remediation priority · High
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
Heap-based buffer overflow in PolarSSL 1.x before 1.2.17 and ARM mbed TLS (formerly PolarSSL) 1.3.x before 1.3.14 and 2.x before 2.1.2 allows remote SSL servers to cause a denial of service (client crash) and possibly execute arbitrary code via a long hostname to the server name indication (SNI) extension, which is not properly handled when creating a ClientHello message. NOTE: this identifier has been SPLIT per ADT3 due to different affected version ranges. See CVE-2015-8036 for the session ticket issue that was introduced in 1.3.0.

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

Heap-based buffer overflow vulnerability in PolarSSL/mbed TLS clients when processing the Server Name Indication (SNI) extension. When a remote SSL server sends a long hostname in the SNI, the client fails to properly bounds-check when building the ClientHello message, causing heap corruption that can lead to crash or arbitrary code execution.

MitigationUpgrade PolarSSL to version 1.2.17+ or mbed TLS to version 1.3.14+ or 2.1.2+ to patch the SNI hostname length validation. Applications using the library as an SSL client connecting to untrusted servers are vulnerable.

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
Debian LinuxOperating system
Affected:= 7.0= 8.0
FedoraOperating system
Affected:= 21= 22= 23
PolarsslApplication
Affected:>= 1.0.0, < 1.2.17
Mbed TlsApplication
Affected:>= 1.3.0, < 1.3.14>= 2.0.0, < 2.1.2
LeapOperating system
Affected:= 42.1
OpensuseOperating system
Affected:= 13.2

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
M
Authentication
None
Confidentiality
Partial
Integrity
Partial
Availability
Partial

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

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 installed PolarSSL or mbed TLS library version
    Run `dpkg -l | grep -i polarssl` on Debian/Ubuntu, `rpm -qa | grep -i polarssl` on Fedora/RHEL, or check the library file with `strings /usr/lib/libpolarssl.so* | grep -i version` or `strings /usr/lib/libmbedtls.so* | grep -i version`
    Affected if The installed version falls within 1.0.0 to 1.2.16 for PolarSSL, 1.3.0 to 1.3.13 for mbed TLS 1.x, or 2.0.0 to 2.1.1 for mbed TLS 2.x
  2. Confirm the library is used for SSL client connections
    Review application code or configuration to verify it uses the PolarSSL/mbed TLS library to initiate SSL/TLS client connections rather than only acting as a server
    Affected if The application uses the library as an SSL client connecting to remote servers
  3. Determine if Server Name Indication (SNI) is enabled
    Check application configuration or source code for SNI usage - look for calls to ssl_set_hostname, ssl_set_sni, or similar SNI-related functions in the client code
    Affected if SNI is enabled and the client sends Server Name Indication during TLS handshake
  4. Verify the client connects to external or untrusted servers
    Review network connections and application behavior to confirm the SSL client connects to servers outside the local network or to potentially untrusted remote servers
    Affected if The vulnerable client connects to remote servers that could send a maliciously crafted SNI extension

You are affected if you have PolarSSL version < 1.2.17, mbed TLS 1.3.x version < 1.3.14, or mbed TLS 2.x version < 2.1.2 installed and your application uses the library as an SSL client with SNI enabled connecting to remote servers.

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
Upgrade available Upgrade to 1.2.17 / 1.3.14 / 2.1.2 or later
Fixed in 1.2.171.3.142.1.2
Interim mitigation

Upgrade PolarSSL to version 1.2.17+ or mbed TLS to version 1.3.14+ or 2.1.2+ to patch the SNI hostname length validation. Applications using the library as an SSL client connecting to untrusted servers are vulnerable.

Fix this in Debian Linux Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing8.0 h
  • Review / QA3.0 h
20.0 hours of engineering $3,420
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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-2015-5291 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