---
title: "CVE-2025-40923\n    | Ubuntu"
description: Ubuntu is an open source software operating system that runs from the
  desktop, to the cloud, to all your internet connected things.
url: https://ubuntu.com/security/CVE-2025-40923?format=md
keywords: index, follow
---

# CVE-2025-40923

Publication date 16 July 2025

Last updated 23 July 2025

---

Ubuntu priority

**Medium**

[Why this priority?](https://ubuntu.com/security/cves/about#priority )

## Cvss 3 Severity Score

**7.3 · High**

[Score breakdown](https://ubuntu.com/security/CVE-2025-40923?format=md#impact-score)

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## Description

Plack-Middleware-Session before version 0.35 for Perl generates session ids
insecurely.
The default session id generator returns a SHA-1 hash seeded with the
built-in rand function, the epoch time, and the PID. The PID will come from
a small set of numbers, and the epoch time may be guessed, if it is not
leaked from the HTTP Date header. The built-in rand function is unsuitable
for cryptographic usage.
Predicable session ids could allow an attacker to gain access to systems.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| libplack-middleware-session-perl | 26.04 LTS resolute | Not affected |
| 25.10 questing | Ignored end of life, was needs-triage |
| 25.04 plucky | Ignored end of life, was needs-triage |
| 24.04 LTS noble | Needs evaluation |
| 22.04 LTS jammy | Needs evaluation |
| 20.04 LTS focal | Needs evaluation |
| 18.04 LTS bionic | Needs evaluation |
| 16.04 LTS xenial | Needs evaluation |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)
* [Patch details](https://ubuntu.com/security/CVE-2025-40923?format=md#patch-details)

### Patch details

For informational purposes only. We recommend not to cherry-pick updates. [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)

| Package | Patch details |
| --- | --- |
| libplack-middleware-session-perl | * Upstream:   [1fbfbb3](https://github.com/plack/Plack-Middleware-Session/commit/1fbfbb355e34e7f4b3906f66cf958cedadd2b9be) |

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

7.3 · High

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | Low |
  | Privileges required | None |
  | User interaction | None |
  | Scope | Unchanged |
  | Confidentiality impact | Low |
  | Integrity impact | Low |
  | Availability impact | Low |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 7.3 · High |
  | Exploitability score | - |
  | Impact score | - |

**Vector:** CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-40923)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2025-40923)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2025-40923)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2025-40923)

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2025-40923>
* <https://lists.security.metacpan.org/cve-announce/msg/31223483/>
* <https://github.com/plack/Plack-Middleware-Session/pull/52>
* <https://metacpan.org/release/MIYAGAWA/Plack-Middleware-Session-0.34/source/lib/Plack/Session/State.pm#L22>
* <https://security.metacpan.org/docs/guides/random-data-for-security.html>