CVE-2011-4126Public exploit

Root privilege escalation via mount-helper symlink race

Published Oct 27, 2021 · Updated Aug 7, 2024

Race condition in calibre's Linux mount helper allows local users to gain root privileges by changing checked symlink targets before mounting. The setuid devices/linux_mount_helper.c helper validates a symlink path and later passes the same mutable path to mount, leaving a check-use window. Exploitation requires local command execution and the upstream setuid helper; a successful race can mount attacker-controlled content over protected paths.

CVSS severity8.1
High
EPSS probability1.54%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in calibre's Linux mount helper allows local users to gain root privileges by changing checked symlink targets before mounting. The setuid devices/linux_mount_helper.c helper validates a symlink path and later passes the same mutable path to mount, leaving a check-use window. Exploitation requires local command execution and the upstream setuid helper; a successful race can mount attacker-controlled content over protected paths.

The record

CVE
CVE-2011-4126
Published
Oct 27, 2021
Updated
Aug 7, 2024
Vendor
Kovid Goyal
Product
calibre
Classifications
CWE-367, T1068
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 27, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 7, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=unknown

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Kovid Goyal · calibreversion=unknown

Published CVSS scores

9.3NIST NVDAV:N/AC:M/Au:N/C:C/I:C/A:C
8.1NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
T1068Exploitation for Privilege Escalation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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