Security readout for executives and security teams
Plain-English summary
CVE-2021-39229 is a denial-of-service flaw in Apprise before 0.9.5.1. If an application exposes Apprise’s built-in IFTTT notification plugin to untrusted input, a crafted value can trigger excessive regular-expression processing and make the service unavailable.
Executive priority
Treat as a high-priority availability risk where Apprise backs customer-facing or operational notification workflows. Patch during the next controlled maintenance window, faster if the IFTTT plugin is internet-facing or accepts untrusted input.
Technical view
Affected Apprise versions before 0.9.5.1 contain an inefficient regular expression in apprise/plugins/NotifyIFTTT.py. The CVSS 3.1 score is 7.5, reflecting network reachability, low complexity, no privileges, no user interaction, and high availability impact only.
Likely exposure
Exposure is likely limited to applications or automation platforms using Apprise versions below 0.9.5.1 where users or remote callers can reach the IFTTT plugin path. Deployments not using or exposing the IFTTT plugin have materially lower practical exposure based on the source bundle.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. The issue is still operationally relevant because the CVSS vector indicates unauthenticated network-triggerable availability impact when the vulnerable plugin is reachable.
Researcher notes
The public bundle identifies CWE-400 and points to the vulnerable regular expression location and the fixing pull request. Evidence supports availability impact, not confidentiality or integrity impact. Do not assume broad exposure without confirming IFTTT plugin reachability in the target application.
Mitigation direction
- Upgrade Apprise to version 0.9.5.1 or later.
- If upgrade is not possible, remove apprise/plugins/NotifyIFTTT.py as vendor-advised mitigation.
- Confirm dependency lockfiles and deployed artifacts no longer contain vulnerable Apprise versions.
- Check vendor advisory and release notes before using alternative mitigations.
Validation and detection
- Inventory applications, containers, and automation jobs that import or package Apprise.
- Check installed Apprise versions and flag anything below 0.9.5.1.
- Determine whether the IFTTT plugin is present and reachable by untrusted users or requests.
- Verify remediation by confirming version 0.9.5.1 or later, or the IFTTT plugin file is absent.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-400: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-39229 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/caronc/apprise/security/advisories/GHSA-qhmp-h54x-38qrCVE reference · x_refsource_CONFIRM
- https://github.com/caronc/apprise/pull/436CVE reference · x_refsource_MISC
- https://github.com/caronc/apprise/blob/0007eade20934ddef0aba38b8f1aad980cfff253/apprise/plugins/NotifyIFTTT.py#L356-L359CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Uncontrolled Resource Consumption
Uncontrolled Resource Consumption represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.