CyberSecBulletin
CVE-2023-27581NVD status: Modified

github-slug-action: Improper Neutralization of Special Elements used in a Command

Published Updated By the CyberSecBulletin desk

CVE-2023-27581 is a high-severity improper neutralization of special elements used in a command vulnerability in github-slug-action from Rlespinasse, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. Affected github-slug-action versions: >= 4.0.0, < 4.4.1. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 1.58% chance of exploitation within 30 days, higher than 76% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Check which version of github-slug-action you run against the affected versions below, and install the vendor's latest release.
  2. Read the advisory on github.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
Rlespinassegithub-slug-action>= 4.0.0, < 4.4.1Not 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
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
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:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.18.8HighCNA (github.com)
CVSS 3.18.8HighNVD

Official description

github-slug-action is a GitHub Action to expose slug value of GitHub environment variables inside of one's GitHub workflow. Starting in version 4.0.0` and prior to version 4.4.1, this action uses the `github.head_ref` parameter in an insecure way. This vulnerability can be triggered by any user on GitHub on any workflow using the action on pull requests. They just need to create a pull request with a branch name, which can contain the attack payload. This can be used to execute code on the GitHub runners and to exfiltrate any secrets one uses in the CI pipeline. A patched action is available in version 4.4.1. No workaround is available.

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

The underlying weakness: Improper Neutralization of Special Elements used in a Command

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

How developers prevent this class of flaw

  • If at all possible, use library calls rather than external processes to recreate the desired functionality.
  • If possible, ensure that all external commands called from the program are statically created.
  • Run time: Run time policy enforcement may be used in an allowlist fashion to prevent use of any non-sanctioned commands.

More Improper Neutralization of Special Elements used in a Command vulnerabilities (CWE-77)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Technical write-ups (may include proof of concept)

Recent Improper Neutralization of Special Elements used in a Command vulnerabilities

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