CyberSecBulletin
CVE-2025-27607NVD status: Analyzed

python-json-logger: Inclusion of Functionality from Untrusted Control Sphere

Published Updated By the CyberSecBulletin desk

CVE-2025-27607 is a high-severity inclusion of functionality from untrusted control sphere vulnerability in python-json-logger from Nhairs, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. Affected python-json-logger versions: >= 3.2.0, < 3.3.0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 1.61% 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 python-json-logger 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.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
  4. Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.

Affected products and versions

VendorProductAffected versionsFixed in
Nhairspython-json-logger>= 3.2.0, < 3.3.0Not 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
RequiredA user must take an action such as opening a file or link.
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:N/UI:R/S:U/C:H/I:H/A:H. Scored by CNA (github.com).

Official description

Python JSON Logger is a JSON Formatter for Python Logging. Between 30 December 2024 and 4 March 2025 Python JSON Logger was vulnerable to RCE through a missing dependency. This occurred because msgspec-python313-pre was deleted by the owner leaving the name open to being claimed by a third party. If the package was claimed, it would allow them RCE on any Python JSON Logger user who installed the development dependencies on Python 3.13 (e.g. pip install python-json-logger[dev]). This issue has been resolved with 3.3.0.

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

The underlying weakness: Inclusion of Functionality from Untrusted Control Sphere

The product imports, requires, or includes executable functionality (such as a library) from a source that is outside of the intended control sphere.

How developers prevent this class of flaw

  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
  • When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs. For example, ID 1 could map to inbox.txt and ID 2 could map to profile.txt. Features such as the ESAPI AccessReferenceMap provide this capability.
  • For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

More Inclusion of Functionality from Untrusted Control Sphere vulnerabilities (CWE-829)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Inclusion of Functionality from Untrusted Control Sphere vulnerabilities

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