CVE-2020-5291 | Privilege escalation in setuid mode via user namespaces in Bubblewrap

Bubblewrap (bwrap) before version 0.4.1, if installed in setuid mode and the kernel supports unprivileged user namespaces, then the `bwrap --userns2` option can be used to make the setuid process keep running as root while being traceable. This can in turn be used to gain root permissions. Note that this only affects the combination of bubblewrap in setuid mode (which is typically used when unprivileged user namespaces are not supported) and the support of unprivileged user namespaces. Known to be affected are: * Debian testing/unstable, if unprivileged user namespaces enabled (not default) * Debian buster-backports, if unprivileged user namespaces enabled (not default) * Arch if using `linux-hardened`, if unprivileged user namespaces enabled (not default) * Centos 7 flatpak COPR, if unprivileged user namespaces enabled (not default) This has been fixed in the 0.4.1 release, and all affected users should update.

Published: 2020-03-31 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-5291 is rated Moderate Risk (48.8/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.91%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2020-5291

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.19% 0.91% +0.72%
2 2025-11-21 0.07% 0.19% +0.12%
3 2025-11-18 — 0.07% —

Full EPSS history (11 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-5291

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.2 3.1 HIGH
CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 0.8 5.8 [email protected]
7.8 3.1 HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 5.9 [email protected]
8.5 2.0 HIGH
AV:N/AC:M/Au:S/C:C/I:C/A:C Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:C)
Complete confidentiality impact.
Integrity impact (I:C)
Complete integrity impact.
Availability impact (A:C)
Complete availability impact.
 6.8 10.0 [email protected]

Weakness enumeration for CVE-2020-5291

OS Trackers for CVE-2020-5291

vendor priority summary link
alpine high CVE-2020-5291: 1 source package rows (bubblewrap); 10 state rows across 10 repos (3.10-main, 3.11-main, 3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 9, open 1. https://security.alpinelinux.org/vuln/CVE-2020-5291
debian low CVE-2020-5291 low priority: Debian including 1 source packages (bubblewrap), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2020-5291
redhat medium — https://access.redhat.com/security/cve/CVE-2020-5291
suse high CVE-2020-5291 severity important: SUSE including 13 source package names (bubblewrap, bubblewrap-0.11.0-150500.3.9.1, …), 18 product×package rows across 12 product lines (SUSE Linux Enterprise Module for Basesystem 15 SP2, SUSE Linux Enterprise Module for Basesystem 15 SP3, … (12 product lines)): Fixed 16, Known Not Affected 2. https://www.suse.com/security/cve/CVE-2020-5291/
ubuntu low CVE-2020-5291 low priority: Ubuntu including 1 source packages (bubblewrap), 7 status rows across 7 suites (bionic, eoan, focal, groovy, trusty, upstream, xenial): released 3, DNE 2, not-affected 2. https://ubuntu.com/security/CVE-2020-5291

Affected software / configurations for CVE-2020-5291

Vendor Product Version Raw CPE
projectatomic bubblewrap < 0.4.1 cpe:2.3:a:projectatomic:bubblewrap:*:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
archlinux arch_linux — cpe:2.3:o:archlinux:arch_linux:-:*:*:*:*:*:*:*
centos centos 7.0 cpe:2.3:o:centos:centos:7.0:*:*:*:*:*:*:*

References for CVE-2020-5291

cvelogic Threat Intelligence