CyberSecBulletin
CVE-2023-0881NVD status: Analyzed

Ubuntu package linux-bluefield: Inefficient Regular Expression Complexity

Published Updated By the CyberSecBulletin desk

CVE-2023-0881 is a high-severity inefficient regular expression complexity vulnerability in Ubuntu package linux-bluefield from Ubuntu, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 5.4.0-1058.64 as the first without the flaw, so updating Ubuntu package linux-bluefield to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.44% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Ubuntu package linux-bluefield to 5.4.0-1058.64 or a later version.
  2. Update Linux-bluefield to 5.4.0-1058.64 or a later version.
  3. 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
UbuntuUbuntu package linux-bluefield5.4.0-1001.2 up to, but not including, 5.4.0-1058.645.4.0-1058.64
CanonicalLinux-bluefieldbefore 5.4.0-1058.645.4.0-1058.64

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
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
NoneNothing can be modified.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA (ubuntu.com).

Official description

Running DDoS on tcp port 22 will trigger a kernel crash. This issue is introduced by the backport of a commit regarding nft_lookup without the subsequent fixes that were introduced after this commit. The resolution of this CVE introduces those commits to the linux-bluefield package.

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

The underlying weakness: Inefficient Regular Expression Complexity

The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.

How developers prevent this class of flaw

  • Use regular expressions that do not support backtracking, e.g. by removing nested quantifiers.
  • Set backtracking limits in the configuration of the regular expression implementation, such as PHP's pcre.backtrack_limit. Also consider limits on execution time for the process.
  • Do not use regular expressions with untrusted input. If regular expressions must be used, avoid using backtracking in the expression.

More Inefficient Regular Expression Complexity vulnerabilities (CWE-1333)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Technical write-ups (may include proof of concept)

Recent Inefficient Regular Expression Complexity vulnerabilities

Spotted an error? Tell us.