Security readout for executives and security teams
Plain-English summary
CVE-2021-3999 is a glibc getcwd() memory corruption flaw that can let a local user gain higher privileges in specific setuid program conditions. It is not a remote internet-facing bug by itself, but it matters on shared Linux systems and servers where local compromise could become full system compromise.
Executive priority
Treat as a high-priority patching issue for Linux fleets with local users, shared access, or sensitive workloads. It is less urgent than a remotely exploitable internet-facing flaw, but privilege escalation can turn a limited foothold into full host compromise.
Technical view
The flaw is an off-by-one buffer overflow and underflow in glibc getcwd() when the supplied buffer size is exactly 1. A local attacker with control over the buffer and size passed by a setuid program could potentially execute arbitrary code and escalate privileges. CVSS 3.1 is 7.8, local vector, low complexity, privileges required.
Likely exposure
Exposure is likely on Linux or vendor appliance environments running vulnerable or unpatched glibc builds, especially multi-user systems. The provided bundle states glibc v2.31 and above are fixed, but distributions may backport fixes, so vendor package advisories should control exposure decisions.
Exploitation context
The bundle does not establish active exploitation, and KEV status is false. Exploitation requires local access and a vulnerable setuid program path that passes attacker-controlled getcwd() inputs. The impact can still be severe because successful exploitation may produce privilege escalation and arbitrary code execution.
Researcher notes
Evidence supports a local privilege-escalation condition in glibc getcwd() tied to buffer size 1 and setuid program misuse. The supplied sources identify the upstream issue, fix references, and downstream advisories. They do not provide evidence of active exploitation or universal product impact.
Mitigation direction
- Apply vendor glibc security updates or confirm an equivalent fixed backport is installed.
- Use distribution advisories rather than upstream version strings alone for patched-package decisions.
- Prioritize shared servers, developer workstations, and systems allowing local shell access.
- Check Red Hat, Debian, NetApp, and other relevant vendor guidance for product-specific status.
- Reduce unnecessary setuid exposure where operationally feasible.
Validation and detection
- Inventory installed glibc packages across Linux hosts and appliances.
- Compare package status with applicable vendor advisories for CVE-2021-3999.
- Confirm vulnerable systems received patched glibc updates and rebooted if required.
- Review high-risk local-user systems for unnecessary setuid-root binaries.
- Track exceptions where vendor guidance is unavailable or incomplete.
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-193: 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 lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-3999 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
- High
- CVSS
- 7.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.8HighVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://www.openwall.com/lists/oss-security/2022/01/24/4CVE reference
- https://sourceware.org/bugzilla/show_bug.cgi?id=28769CVE reference
- https://sourceware.org/git/gitweb.cgi?p=glibc.git%3Bh=23e0e8f5f1fb5ed150253d986ecccdc90c2dcd5eCVE reference
- https://bugzilla.redhat.com/show_bug.cgi?id=2024637CVE reference
- https://access.redhat.com/security/cve/CVE-2021-3999CVE reference
- https://security-tracker.debian.org/tracker/CVE-2021-3999CVE reference
- [debian-lts-announce] 20221017 [SECURITY] [DLA 3152-1] glibc security updateCVE reference · mailing-list
- https://security.netapp.com/advisory/ntap-20221104-0001/CVE reference
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.
Off-by-one Error
Off-by-one Error represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.