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Ubuntu LinuxOperating system · Canonical

CVE-2021-32554

MEDIUM · 5.5 CVSS v3.1 Published 2021-06-12
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
57/100
Remediation priority · Elevated
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
It was discovered that read_file() in apport/hookutils.py would follow symbolic links or open FIFOs. When this function is used by the xorg package apport hooks, it could expose private data to other local users.

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 read_file() function in apport/hookutils.py does not properly validate file types before opening them, allowing it to follow symbolic links and open FIFOs (named pipes). When xorg package apport hooks use this function, an attacker with local access could exploit this behavior to read private data belonging to other local users.

MitigationUpdate apport to a version that implements proper validation in read_file() to reject symbolic links and FIFOs, or temporarily disable xorg apport hooks until a patch is available.

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
Ubuntu LinuxOperating system
Affected:= 18.04= 20.04= 20.10= 21.04= 21.10

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
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

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

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. Verify apport package is installed
    Run `dpkg -l | grep apport` or `apt list --installed | grep apport` to check if the apport package is present on the system
    Affected if apport is installed and the system is Ubuntu 18.04, 20.04, 20.10, 21.04, or 21.10
  2. Check installed apport version
    Run `dpkg -s apport` and note the Version field, or run `apport-cli --version`
    Affected if The installed version matches one of the affected Ubuntu releases (18.04, 20.04, 20.10, 21.04, 21.10) and has not been patched to fix the read_file() validation issue
  3. Verify xorg apport hooks are enabled
    Check for the presence of hook files in /etc/apport/report-hooks/ or /usr/share/apport/package-hooks/, specifically look for xorg-related hook files
    Affected if xorg apport hooks exist and are active, enabling the vulnerable read_file() function to be called when processing xorg crash reports
  4. Inspect the vulnerable read_file() function
    Examine /usr/lib/python3/dist-packages/apport/hookutils.py (or the equivalent path on your system) and look at the read_file() function for lack of stl_mode and file type validation
    Affected if The read_file() function lacks proper validation to reject symbolic links and FIFOs before opening files
  5. Test for symlink/FIFO following behavior
    As a test (non-destructive), create a test file and a symlink to it, then call the read_file() function if accessible via Python to observe whether symlinks are followed
    Affected if The function follows symbolic links and opens non-regular files, confirming the vulnerability is present

A user is affected if they are running an unpatched apport version on Ubuntu 18.04 through 21.10 with xorg apport hooks enabled, and the read_file() function in hookutils.py lacks file type validation.

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
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Update apport to a version that implements proper validation in read_file() to reject symbolic links and FIFOs, or temporarily disable xorg apport hooks until a patch is available.

Fix this in Ubuntu Linux Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,190
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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-2021-32554 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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