dbcve.org
GlibcFramework / library · Gnu

CVE-2026-6238

MEDIUM · 6.5 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 →
74/100
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 deprecated functions ns_printrrf, ns_printrr and fp_nquery in the GNU C Library version 2.0.1 to version 2.43 fail to validate the RDATA content against the RDATA length in a DNS response when processing A6, CERT, LOC, TKEY or TSIG records, which may allow an attacker to craft a DNS response, causing a target application to crash or read uninitialized memory. These functions are for application debugging only and hence not in the path of code executed by the DNS resolver. Further, they have been deprecated since version 2.34 and should not be used by any new applications. Applications should consider porting away from these interfaces since they may be removed in future versions.

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 glibc functions ns_printrrf, ns_printrr, and fp_nquery fail to validate RDATA content against RDATA length when processing A6, CERT, LOC, TKEY, or TSIG DNS records, potentially allowing crafted DNS responses to trigger out-of-bounds reads or crashes. These debugging functions are not in the normal DNS resolver code path and were deprecated in glibc 2.34.

MitigationMigrate applications away from these deprecated debugging functions. If continued use is unavoidable, implement application-level validation of DNS response RDATA lengths before passing data to these functions, and monitor for glibc security updates.

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
None
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/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 `ldconfig -v` to identify the installed glibc version. Alternatively, check /lib/x86_64-linux-gnu/libc.so.6 or /lib/libc.so.6 for the version string.
    Affected if The installed glibc version is 2.2 or higher AND the application uses the deprecated functions (see next steps). Note: functions were deprecated in glibc 2.34.
  2. Detect usage of vulnerable functions in application code
    Search application binaries and shared libraries for references to ns_printrrf, ns_printrr, or fp_nquery using `nm -D <binary>` or `strings <binary> | grep -E 'ns_printrrf|ns_printrr|fp_nquery'`. Check also for static linking of libbind that may expose these functions.
    Affected if The application binary or its dependencies link to or call ns_printrrf, ns_printrr, or fp_nquery.
  3. Identify if application processes the affected DNS record types
    Review application source code or documentation to determine if it processes DNS A6, CERT, LOC, TKEY, or TSIG record types, especially through debugging, logging, or diagnostic code paths.
    Affected if The application processes any of these DNS record types AND uses the deprecated functions from step 2.
  4. Verify function is in code path during DNS response handling
    Trace or analyze application execution to determine if the deprecated functions are actually invoked during DNS response parsing, particularly when handling the affected record types.
    Affected if The deprecated functions are called at runtime when processing A6, CERT, LOC, TKEY, or TSIG DNS records.

The environment is affected only if the installed glibc is version 2.2 or higher AND the application actively uses ns_printrrf, ns_printrr, or fp_nquery functions to process A6, CERT, LOC, TKEY, or TSIG DNS records in the code path.

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

Migrate applications away from these deprecated debugging functions. If continued use is unavoidable, implement application-level validation of DNS response RDATA lengths before passing data to these functions, and monitor for glibc security updates.

Recommended fix Moderate confidence

glibc > 2.43 (or latest stable release)

  1. 1. Identify applications that use the deprecated functions ns_printrrf, ns_printrr, or fp_nquery by searching source code for these function names.
  2. 2. Review each application to determine if these debugging functions are actually needed; if not, remove the usage.
  3. 3. If these functions are still required, plan to migrate to alternative debugging approaches or updated APIs.
  4. 4. Upgrade glibc on affected systems to a version newer than 2.43 where the vulnerability is patched.
  5. 5. After upgrading, rebuild any statically linked applications that may have been compiled against the older glibc.
Caveat Applications using these deprecated functions will need to be updated; upgrade may introduce compatibility changes in other glibc behaviors

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

Fix this in Glibc Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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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-2026-6238 in production — separate from our analysis above.

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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
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