CyberSecBulletin
CVE-2023-1523NVD status: Modified

snapd: Improper Neutralization of Special Elements in Output Used by a Downstream Component

Published Updated By the CyberSecBulletin desk

CVE-2023-1523 is a critical-severity improper neutralization of special elements in output used by a downstream component vulnerability in snapd from Canonical, with a CVSS 3.1 base score of 10.0 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. There is no confirmed exploitation so far. EPSS estimates a 1.45% chance of exploitation within 30 days, higher than 74% of scored CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Check which version of snapd you run against the affected versions below, and install the vendor's latest release.
  2. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
CanonicalsnapdNot specified in the recordNot stated
CanonicalUbuntu Linux16.04; 18.04; 20.04; 22.04; 22.10; 23.04Not stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
ChangedThe attack can reach beyond the vulnerable component into other systems.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.110.0CriticalCNA (ubuntu.com)
CVSS 3.110.0CriticalNVD

Official description

Using the TIOCLINUX ioctl request, a malicious snap could inject contents into the input of the controlling terminal which could allow it to cause arbitrary commands to be executed outside of the snap sandbox after the snap exits. Graphical terminal emulators like xterm, gnome-terminal and others are not affected - this can only be exploited when snaps are run on a virtual console.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Neutralization of Special Elements in Output Used by a Downstream Component

The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.

How developers prevent this class of flaw

  • Programming languages and supporting technologies might be chosen which are not subject to these issues.
  • Utilize an appropriate mix of allowlist and denylist parsing to filter control-plane syntax from all input.

More Improper Neutralization of Special Elements in Output Used by a Downstream Component vulnerabilities (CWE-74)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: poc, automatable: yes, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Patches and release notes

Third-party and government advisories

Technical write-ups (may include proof of concept)

Other vulnerabilities in snapd

All snapd vulnerabilities

Recent Improper Neutralization of Special Elements in Output Used by a Downstream Component vulnerabilities

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