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X Font ServerApplication · X.org

CVE-2007-4990

HIGH · 7.5 CVSS v2.0 Published 2007-10-05
Fix available
A fix is available. Upgrade to after 1.0.4 or later.
See remediation →
84/100
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 swap_char2b function in X.Org X Font Server (xfs) before 1.0.5 allows context-dependent attackers to execute arbitrary code via (1) QueryXBitmaps and (2) QueryXExtents protocol requests with crafted size values that specify an arbitrary number of bytes to be swapped on the heap, which triggers heap corruption.

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 buffer overflow vulnerability in X.Org X Font Server (xfs) allows remote attackers to execute arbitrary code via crafted QueryXBitmaps and QueryXExtents protocol requests that manipulate size values to trigger excessive byte swapping on the heap, corrupting memory.

MitigationUpgrade xfs to version 1.0.5 or later to obtain the patched swap_char2b function with proper bounds validation; if upgrading is not feasible, apply source-level patch to swap_char2b to validate size parameters before performing byte-swapping operations.

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
X Font ServerApplication
Affected:<= 1.0.4

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
Partial
Availability
Partial

AV:N/AC:L/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. Check if xfs package is installed
    On RHEL/CentOS: rpm -qa | grep -i xfs. On Debian/Ubuntu: dpkg -l | grep -i xfs. Or use: which xfs
    Affected if No xfs package found means not affected by this specific vulnerability
  2. Determine installed xfs version
    Run: xfs -version 2>&1 or rpm -q xfs (RHEL) / dpkg -s xfs (Debian)
    Affected if Version number returned is 1.0.4 or lower indicates vulnerable version
  3. Check if xfs daemon is running
    Run: ps aux | grep xfs or systemctl status xfs (or check /etc/init.d/xfs status on older systems)
    Affected if xfs daemon is actively running means the attack surface is present; even if vulnerable version is installed but not running, the immediate risk is reduced
  4. Verify xfs network exposure
    Check if xfs is listening on network ports: netstat -anp | grep xfs or ss -anp | grep xfs. Default xfs port is 7100.
    Affected if xfs is bound to network interfaces (0.0.0.0) exposes the service to remote attackers; local-only (127.0.0.1) reduces exposure

Environment is affected if xfs version 1.0.4 or lower is installed AND the xfs daemon is running and accessible, allowing malicious QueryXBitmaps/QueryXExtents protocol requests to reach the vulnerable swap_char2b function.

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 1.0.4
Interim mitigation

Upgrade xfs to version 1.0.5 or later to obtain the patched swap_char2b function with proper bounds validation; if upgrading is not feasible, apply source-level patch to swap_char2b to validate size parameters before performing byte-swapping operations.

Fix this in X Font Server Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing1.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,090
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,744.

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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-2007-4990 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
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