dbcve.org
GlibcFramework / library · Gnu

CVE-2026-5435

HIGH · 7.3 CVSS v3.1 Published 2026-04-28
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
82/100
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
The deprecated functions ns_printrrf, ns_printrr and fp_nquery in the GNU C Library version 2.2 and newer fail to enforce the caller-supplied buffer length, and can result in an out-of-bounds write when printing TSIG records.

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

The deprecated DNS functions ns_printrrf, ns_printrr, and fp_nquery in glibc versions 2.2 and newer lack proper buffer length validation when handling TSIG records, allowing out-of-bounds writes that could enable remote code execution or service disruption.

MitigationReplace usage of these deprecated functions with modern, buffer-safe alternatives in the DNS implementation, or upgrade to a glibc version that includes bounds checking fixes for these functions.

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
GlibcFramework / library
Affected:>= 2.2

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
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

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. Check glibc version
    Run 'ldd --version' or '/lib/libc.so.6 --version' to retrieve the installed glibc version number
    Affected if The reported glibc version is 2.2 or newer (versions 2.2 through the current version are affected)
  2. Identify processes using deprecated DNS functions
    Search application binaries and libraries for references to 'ns_printrrf', 'ns_printrr', or 'fp_nquery' using 'nm -D <binary>' or 'grep -r "ns_printrrf\|ns_printrr\|fp_nquery" <path>'
    Affected if Any loaded library or application code actively calls these deprecated functions
  3. Verify TSIG record processing is enabled
    Review application configuration files or runtime environment to determine if the code path processing DNS TSIG records is active (check for 'tsig', 'update', or 'transfer' related DNS configurations)
    Affected if The environment processes DNS TSIG records through the vulnerable code path
  4. Check for dynamic linkage to vulnerable glibc
    Use 'ldd <executable>' to list linked glibc version, or check '/etc/ld.so.conf' and '/etc/ld.so.cache' for glibc library paths
    Affected if The process links to a glibc version 2.2 or newer that contains the vulnerable functions

You are affected if your system runs glibc version 2.2 or newer AND any application or service actively uses the deprecated ns_printrrf, ns_printrr, or fp_nquery functions to process DNS TSIG records.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Replace usage of these deprecated functions with modern, buffer-safe alternatives in the DNS implementation, or upgrade to a glibc version that includes bounds checking fixes for these functions.

Recommended fix Moderate confidence

Latest stable glibc release (typically glibc 2.40+ in 2024-2025, check sourceware.org for current stable release)

  1. Identify the current glibc version on your system using: rpm -q glibc or dpkg -l | grep libc6
  2. Check if your operating system vendor has released a security advisory for this CVE
  3. If a vendor patch is available, apply it through your system's package manager (e.g., yum update glibc or apt-get update && apt-get install libc6)
  4. If no vendor patch exists, upgrade to the latest stable glibc release from sourceware.org/glibc/
  5. After upgrading, reboot the system to ensure the new glibc is loaded
  6. Verify the fix by checking the glibc version and confirming the vulnerable functions are no longer present or have been patched
Caveat Upgrading glibc is a major system change; always test in a non-production environment first as it may affect system compatibility and require rebuilding dependent applications

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Glibc Scoped from the published advisory
  • Consultation8.0 h
  • Implementation16.0 h
  • Testing8.0 h
  • Review / QA4.0 h
36.0 hours of engineering $6,400
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $10,240.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2026-5435 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2026-5435 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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