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Debian LinuxOperating system · Debian

CVE-2015-1781

MEDIUM · 6.8 CVSS v2.0 Published 2015-09-28
Fix available
A fix is available. Upgrade to after 2.21 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
Buffer overflow in the gethostbyname_r and other unspecified NSS functions in the GNU C Library (aka glibc or libc6) before 2.22 allows context-dependent attackers to cause a denial of service (crash) or execute arbitrary code via a crafted DNS response, which triggers a call with a misaligned buffer.

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

Buffer overflow in glibc's NSS functions (gethostbyname_r and related functions) allows context-dependent attackers to execute arbitrary code or cause denial of service via crafted DNS responses that trigger calls with misaligned buffers.

MitigationUpdate glibc to version 2.22 or later to patch the vulnerability; apply vendor-specific security updates for affected systems.

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
Ubuntu LinuxOperating system
Affected:= 12.04= 14.04= 15.04
Linux Enterprise DebuginfoApplication
Affected:= 11
Linux Enterprise DesktopOperating system
Affected:= 11
Linux Enterprise ServerOperating system
Affected:= 11
GlibcFramework / library
Affected:<= 2.21

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 glibc version
    Run `ldd --version` or check `/lib/x86_64-linux-gnu/libc.so.6` (path varies by architecture) using `libc.so.6 --version`
    Affected if glibc version is 2.21 or earlier
  2. Confirm NSS functions in use
    Check if applications use gethostbyname_r, gethostbyname, or related NSS resolver functions. Search binary executables with `nm` or `objdump` for these symbols if needed
    Affected if the system runs any application that performs hostname resolution via glibc's NSS
  3. Verify DNS resolution is active
    Check /etc/nsswitch.conf for 'hosts' line and confirm DNS resolution is enabled (look for 'dns' in the resolution chain)
    Affected if DNS resolution is configured in the system's NSSwitch configuration
  4. Assess network exposure
    Determine if the system processes untrusted DNS responses (internal DNS servers with limited exposure reduce but do not eliminate risk)
    Affected if the system processes DNS responses from untrusted or public networks

A system is affected if it runs glibc version 2.21 or earlier and performs hostname resolution via NSS functions, particularly with exposure to untrusted DNS responses.

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 a release after 2.21
Interim mitigation

Update glibc to version 2.22 or later to patch the vulnerability; apply vendor-specific security updates for affected systems.

Fix this in Debian Linux Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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Scan for this in your stack

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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-2015-1781 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