VulnerabilityPublished 28 Nov 2019Updated 9 Jun 2025

CVE-2019-18276: GNU Bash · Improper Check for Dropped Privileges

Source CVE Database V5

Not known to be exploited · CVSS 7.8 High.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score

7.8High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 2.6% chance of exploitation in 30 days – higher than 85% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Local
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Nov 2019
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
GitHubbminor/bash`pkg:github/bminor/bash`Other threats	Affected <=5.0-patch11	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should apply the following specific mitigation measures: 1) Upgrade GNU Bash to versions later than 5.0 patch 11 where this vulnerability is fixed. If immediate patching is not feasible, consider temporarily restricting the use of Bash shells with differing effective and real UIDs. 2) Implement strict access controls to limit who can execute shell commands, especially with non-root privileges, to reduce the risk of attackers gaining initial shell access. 3) Monitor and restrict the use of the 'enable -f' command or disable runtime loading of builtins where possible, as this is the vector used to regain privileges. 4) Employ mandatory access control frameworks such as SELinux or AppArmor to constrain Bash's ability to load arbitrary shared objects or invoke setuid(). 5) Conduct regular audits of user accounts and running processes to detect unusual privilege escalations or unexpected shared object loads. 6) Harden systems by minimizing the number of users with shell access and employing multi-factor authentication for remote access. 7) Use intrusion detection systems to monitor for suspicious shell activity indicative of exploitation attempts. These targeted steps go beyond generic advice by focusing on controlling the specific exploitation technique and limiting the attack surface related to privilege dropping and regaining in Bash.

Description

An issue was discovered in disable_priv_mode in shell.c in GNU Bash through 5.0 patch 11. By default, if Bash is run with its effective UID not equal to its real UID, it will drop privileges by setting its effective UID to its real UID. However, it does so incorrectly. On Linux and other systems that support "saved UID" functionality, the saved UID is not dropped. An attacker with command execution in the shell can use "enable -f" for runtime loading of a new builtin, which can be a shared object that calls setuid() and therefore regains privileges. However, binaries running with an effective UID of 0 are unaffected.

Impact

For European organizations, this vulnerability presents a serious risk especially in multi-user systems, shared hosting environments, and servers where Bash shells are used with privilege separation mechanisms. An attacker who gains limited shell access could escalate privileges to those of the original user, potentially leading to full system compromise if the original user has elevated rights. This could result in unauthorized data access, modification, or disruption of critical services. Organizations relying on Bash for automation, scripting, or remote shell access may find their systems vulnerable to lateral movement and privilege escalation attacks. The impact is heightened in sectors with sensitive data such as finance, healthcare, and government institutions across Europe, where data confidentiality and system integrity are paramount. Additionally, the vulnerability could be exploited to bypass security controls that rely on privilege separation, undermining defense-in-depth strategies. Although root-level binaries are unaffected, the ability to regain privileges from a dropped state can facilitate further attacks, including persistence, data exfiltration, or deployment of ransomware. Given the widespread use of Bash in Linux-based systems common in European IT infrastructure, the threat is significant and warrants prompt remediation.

CWE-273Improper Check for Dropped Privileges (opens in a new tab)
Base weaknessLikelihood of exploit: Medium
The product attempts to drop privileges but does not check or incorrectly checks to see if the drop succeeded.
Architecture and Design · Separation of Privilege
Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
Implementation
Check the results of all functions that return a value and verify that the value is expected.
Implementation
In Windows, make sure that the process token has the SeImpersonatePrivilege(Microsoft Server 2003). Code that relies on impersonation for security must ensure that the impersonation succeeded, i.e., that a proper privilege demotion happened.
OWASP Cheat Sheets
Docker Security (opens in a new tab)
OWASP ASVS 4.0.3
V11.1.7 (opens in a new tab)
V1.4.4 (opens in a new tab)
V1.4.5 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 10 Jul 2025, 21:03 UTC

WeaknessesCWE-273

Technical details

References

Community reviews

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