How severe is CVE-2020-5205?

CVE-2020-5205 has a CVSS score of 5.4/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2020-5205?

CVE-2020-5205 affects the following packages: pow (Hex). Ecosystems affected: Hex.

How do I fix CVE-2020-5205?

Update pow to 1.0.16 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-5205 is resolved across your whole dependency graph.

How do I detect CVE-2020-5205 in my Hex dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pow, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2020-5205 if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is CVE-2020-5205 actively exploited in the wild?

No public exploit code has been indexed for CVE-2020-5205 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2020-5205?

CVE-2020-5205 has an EPSS (Exploit Prediction Scoring System) score of 0.8%, placing it in the 56th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2020-5205?

CVE-2020-5205 is classified as CWE-384 (CWE-384). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2020-5205 published, and has it been updated?

CVE-2020-5205 was published on January 9, 2020 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

💧

💧 Hex

Not in CISA KEV

MEDIUM severity

CVE-2020-5205 — pow

MEDIUMFix: danschultzer/pow@578ffd3

CVE-2020-5205 is a medium-severity (CVSS 5.4) CWE-384 vulnerability in pow. A fix is available for pow — see the affected versions and patch details below.

Session fixation

Also known asGHSA-v2wf-c3j6-wpvw

Published

Jan 9, 2020

Updated

Oct 20, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 2, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.8%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs56th percentile — riskier than 56% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

💧pow

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Hex packages — download data is not available via public APIs for these ecosystems.

Description

Impact

The use of Plug.Session in Pow.Plug.Session is susceptible to session fixation attacks if a persistent session store is used for Plug.Session, such as Redis or a database. Cookie store, which is used in most Phoenix apps, doesn't have this vulnerability.

Workarounds

Call Plug.Conn.configure_session(conn, renew: true) periodically and after privilege change. A custom authorization plug can be written where the create/3 method should return the conn only after Plug.Conn.configure_session/2 have been called on it.

References

https://github.com/danschultzer/pow/commit/578ffd3d8bb8e8a26077b644222186b108da474f
https://www.owasp.org/index.php/Session_fixation

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
💧Hex	`pow`	all versions	1.0.16`mix deps.update pow`

Affected Products

1 product · 1 configurations

Application

powpowauth

< 1.0.16

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pow, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update pow to 1.0.16 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-5205 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

### Impact The use of `Plug.Session` in `Pow.Plug.Session` is susceptible to session fixation attacks if a persistent session store is used for `Plug.Session`, such as Redis or a database. Cookie store, which is used in most Phoenix apps, doesn't have this vulnerability. ### Workarounds Call `Plug.Conn.configure_session(conn, renew: true)` periodically and after privilege change. A custom authorization plug can be written where the `create/3` method should return the `conn` only after `Plug.Conn.configure_session/2` have been called on it. ### References https://github.com/danschultzer/pow