How severe is CVE-2021-39229?

CVE-2021-39229 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-39229?

CVE-2021-39229 affects the following packages: apprise (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2021-39229?

Update apprise to 0.9.5.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-39229 is resolved across your whole dependency graph.

How do I detect CVE-2021-39229 in my PyPI dependencies?

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

How do I mitigate CVE-2021-39229 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2021-39229 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-39229, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-39229?

CVE-2021-39229 has an EPSS (Exploit Prediction Scoring System) score of 1.9%, placing it in the 79th 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-2021-39229?

CVE-2021-39229 is classified as Uncontrolled Resource Consumption (CWE-400). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-39229 published, and has it been updated?

CVE-2021-39229 was published on September 20, 2021 and was last updated on August 7, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍

🐍 PyPI

Not in CISA KEV

HIGH severity

CVE-2021-39229 — apprise

HIGHFix: caronc/apprise#436

CVE-2021-39229 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in apprise. 1 public exploit reference exists, so weaponization risk is real. A fix is available for apprise — see the affected versions and patch details below.

Apprise vulnerable to regex injection with IFTTT Plugin

Also known asGHSA-qhmp-h54x-38qrPYSEC-2021-327

Published

Sep 20, 2021

Updated

Aug 7, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

1 known

Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.9%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs79th percentile — riskier than 79% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2021-39229 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

🐍apprise

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

Description

Impact

Anyone publicly hosting the Apprise library and granting them access to the IFTTT notification service.

Patches

Update to Apprise v0.9.5.1

# Install Apprise v0.9.5.1 from PyPI
pip install apprise==0.9.5.1

The patch to the problem was performed here.

Workarounds

Alternatively, if upgrading is not an option, you can safely remove the following file:

apprise/plugins/NotifyIFTTT.py

The above will eliminate the ability to use IFTTT, but everything else will work smoothly.

For more information

If you have any questions or comments about this advisory:

Open an issue in Apprise
Email me at [email protected]

Additional Credit

Github would not allow me to additionally credit Rasmus Petersen, but I would like to put that here at the very least - thank you for finding and reporting this issue along with those already credited

Additional Notes:

Github would not allow me to add/tag the 2 CWE's this issue is applicable to (only CWE-400). The other is: CWE-730 (placed in the title)

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`apprise`	all versions	0.9.5.1`pip install --upgrade 'apprise==0.9.5.1'`

Affected Products

1 product · 1 configurations

Application

apprisenuxref

< 0.9.5.1

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Apprise is an open source library which allows you to send a notificatio…

github.comNVDOct 2021

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for apprise, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update apprise to 0.9.5.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-39229 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

### Impact Anyone _publicly_ hosting the Apprise library and granting them access to the IFTTT notification service. ### Patches Update to Apprise v0.9.5.1 ```bash # Install Apprise v0.9.5.1 from PyPI pip install apprise==0.9.5.1 ``` The patch to the problem was performed [here](https://github.com/caronc/apprise/pull/436/files). ### Workarounds Alternatively, if upgrading is not an option, you can safely remove the following file: - `apprise/plugins/NotifyIFTTT.py` The above will eliminate the ability to use IFTTT, but everything else will work smoothly. ### For more informat