Security readout for executives and security teams
Plain-English summary
CVE-2020-8833 is a local privilege-escalation flaw in Ubuntu's Apport crash-reporting tool. A low-privileged local user may abuse a timing race during crash-file cleanup, but only under specific conditions, including disabled symlink protections. Business urgency is moderate, highest on shared Ubuntu systems.
Executive priority
Treat as a moderate-priority Linux hardening and patching item. It is not remotely exploitable from the provided evidence, but it can matter on shared systems where a local foothold could become higher privilege.
Technical view
Apport had a CWE-367 time-of-check/time-of-use race around crash report permission changes. The source describes a race between open and ownership-change operations during cleanup of zero-size crash files. If fs.protected_symlinks is disabled, a local user could influence ownership handling and create a privilege-escalation opportunity.
Likely exposure
Exposure is limited to Ubuntu systems running affected Canonical Apport versions 2.20.1, 2.20.9, or 2.20.11 before the listed fixed builds. Risk is higher where untrusted users have local accounts and fs.protected_symlinks has been disabled.
Exploitation context
The CVSS vector is local, high-complexity, low-privilege, no user interaction, with changed scope and high confidentiality impact. The provided bundle does not show active exploitation, and KEV is false. Exploitation depends on a race condition and a non-default protective setting being disabled.
Researcher notes
The key conditions are local access, a TOCTOU window in Apport cleanup, and disabled symlink protection. The sources name fixed versions but do not provide broader exploit telemetry. Avoid assuming exposure outside Canonical Apport on Ubuntu without vendor evidence.
Mitigation direction
- Upgrade Apport to the fixed Ubuntu package versions listed in the advisory.
- Keep fs.protected_symlinks enabled unless vendor guidance explicitly requires otherwise.
- Prioritize shared servers, developer workstations, and multi-user Ubuntu hosts.
- Review Ubuntu USN-4315-1 and USN-4315-2 for distribution-specific update guidance.
Validation and detection
- Inventory Ubuntu hosts for installed Apport versions.
- Confirm affected systems have received the relevant Ubuntu security update.
- Verify fs.protected_symlinks is not disabled on in-scope hosts.
- Identify systems where untrusted local users can log in.
- Check vendor advisories for any release-specific package names or follow-up guidance.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-367: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupPrivilege behavior lookup
The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2020-8833 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.6 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N1.14Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.6MediumVector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://usn.ubuntu.com/4315-1/CVE reference · x_refsource_CONFIRM
- https://bugs.launchpad.net/ubuntu/+source/apport/+bug/1862933CVE reference · x_refsource_CONFIRM
- USN-4315-2CVE reference · vendor-advisory, x_refsource_UBUNTU
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Time-of-check Time-of-use (TOCTOU) Race Condition
Time-of-check Time-of-use (TOCTOU) Race Condition represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.