CVE-2026-9323: Software Security Vulnerability Vulnerability

CRITICAL
Advisory Identifier: GHSA-83x9-8wvq-rrcp
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CVSS 8.1
CWE-338
Published
Advisory Summary

CVE-2026-9323 is a CRITICAL (CVSS 8.1) security vulnerability vulnerability (CWE-338: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product uses a pseudo-random number generator (prng) in a security context, but the prng's algorithm is not cryptographically strong.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-9323 at a Glance

CVE Identifier CVE-2026-9323
GHSA Identifier GHSA-83x9-8wvq-rrcp
Severity CRITICAL
CVSS v3.1 Base Score 8.1
CWE Classification CWE-338: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 8.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2026-9323

To remediate this vulnerability, upgrade all affected Software dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-9323, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree

Analyze the terminal output to locate any version of Software in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The mvn dependency:tree command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-338: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG), where the product uses a pseudo-random number generator (prng) in a security context, but the prng's algorithm is not cryptographically strong. In Software, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

The urwid web display backend (urwid/display/web.py) generates web session identifiers (urwid_id) in Screen.start() by concatenating two random.randrange(10**9) calls that use Python's Mersenne Twister PRNG, which is not cryptographically secure. Each call consumes approximately 30 bits of PRNG state, and the Mersenne Twister internal state is approximately 19,937 bits, so an attacker who observes approximately 334 session IDs (for example via the X-Urwid-ID HTTP response header) can fully reconstruct the internal state and predict all past and future session IDs (Path B). The same identifier is also used as the filename of a FIFO created in the world-listable /tmp directory (for example /tmp/urwid375487765176907690.in), so any local user on the host can list /tmp to enumerate active session tokens directly (Path A). With a valid session ID, an attacker can read the victim's terminal screen via the polling endpoint, inject keystrokes into the victim's session (yielding OS-level code execution with the session owner's privileges if the session runs a shell), and inject exit sequences or flood the FIFO to terminate or crash the session. A prior Bandit S311 warning on this usage was suppressed with # noqa: S311 rather than fixed

References

GitHub Advisory / Wiki ADVISORY
https://github.com/urwid/urwid/security/advisories/GHSA-rjwp-g85x-gmjv
NVD — CVE-2026-9323 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-9323
Software Source Repository REPOSITORY
https://github.com/urwid/urwid/issues/1127
Software Source Repository REPOSITORY
https://github.com/urwid/urwid/pull/1128
Security Fix Commit FIX COMMIT
https://github.com/urwid/urwid/commit/24acd12f0d0598036d0d577f2ee63e4a27b4a3d9
Software Source Repository REPOSITORY
https://github.com/urwid/urwid
www.vulncheck.com/advisories/insecure... WEB
https://www.vulncheck.com/advisories/insecure-prng-and-information-exposure-in-urwid-web-display-backend

Frequently Asked Questions

What is CVE-2026-9323?
CVE-2026-9323 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-338: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG).
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-9323?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-9323?
CVE-2026-9323 has a CVSS v3.1 base score of 8.1 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-9323?
CVE-2026-9323 is classified under CWE-338: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG) (The product uses a Pseudo-Random Number Generator (PRNG) in a security context, but the PRNG's algorithm is not cryptographically strong.).
How can I check Maven dependencies for CVE-2026-9323?
Run the dependency tree command: 'mvn dependency:tree'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-83x9-8wvq-rrcp",
  "modified" : "2026-07-18T15:31:50Z",
  "published" : "2026-07-18T15:31:50Z",
  "aliases" : [ "CVE-2026-9323" ],
  "details" : "The urwid web display backend (urwid/display/web.py) generates web session identifiers (urwid_id) in Screen.start() by concatenating two random.randrange(10**9) calls that use Python's Mersenne Twister PRNG, which is not cryptographically secure. Each call consumes approximately 30 bits of PRNG state, and the Mersenne Twister internal state is approximately 19,937 bits, so an attacker who observes approximately 334 session IDs (for example via the X-Urwid-ID HTTP response header) can fully reconstruct the internal state and predict all past and future session IDs (Path B). The same identifier is also used as the filename of a FIFO created in the world-listable /tmp directory (for example /tmp/urwid375487765176907690.in), so any local user on the host can list /tmp to enumerate active session tokens directly (Path A). With a valid session ID, an attacker can read the victim's terminal screen via the polling endpoint, inject keystrokes into the victim's session (yielding OS-level code execution with the session owner's privileges if the session runs a shell), and inject exit sequences or flood the FIFO to terminate or crash the session. A prior Bandit S311 warning on this usage was suppressed with # noqa: S311 rather than fixed",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"
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  } ],
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  "references" : [ {
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  }, {
    "type" : "ADVISORY",
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  }, {
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    "url" : "https://github.com/urwid/urwid"
  }, {
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    "url" : "https://www.vulncheck.com/advisories/insecure-prng-and-information-exposure-in-urwid-web-display-backend"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-338" ],
    "severity" : "CRITICAL",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-07-18T14:17:12Z"
  }
}