VulnerabilityPublished 13 Aug 2026Updated 9 Nov 2026

CVE-2026-21441: Icloudpd · Decompression-bomb safeguards bypassed when following HTTP redirects (streaming API)

Affects icloudpdSource GCVE Database

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Not known to be exploited · CVSS 7.5 High : upgrade to 1.33.0 soon.

Data as of 9 Nov 2026, 19:47 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 1.33.0

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 13 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 9 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade icloudpd to 1.33.0.

Affected software

Product	Affected	Fixed in
Homebrewicloudpd`pkg:brew/icloudpd`Other threats	Affected >=1.17.3 <1.33.0	Fixed in 1.33.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade icloudpd to version 1.33.0 or later, which includes the fix that prevents decompressing redirect response content when preload_content=False. If immediate upgrade is not possible, disable HTTP redirects by setting redirect=False in urllib3 requests to untrusted sources to avoid triggering the decompression bomb vulnerability.

Description

A vulnerability in icloudpd versions >=1.17.3 and <1.33.0 allows bypassing decompression-bomb safeguards when following HTTP redirects using urllib3's streaming API. The issue occurs because urllib3 decompresses the entire response body of redirect responses before any read methods are called, without respecting configured read limits. This can lead to excessive CPU and memory consumption, potentially causing denial of service. The vulnerability is fixed in icloudpd version 1.33.0.

Impact

This vulnerability can cause denial of service through resource exhaustion (high CPU and memory usage) on clients processing HTTP redirects with compressed content. There is no impact on confidentiality or integrity. The CVSS v3.1 score is 7.5 (high) with network attack vector, low attack complexity, no privileges required, no user interaction, and impact limited to availability.

Summary

The vulnerability arises from urllib3's handling of HTTP redirect responses when using its streaming API with preload_content set to False. Normally, urllib3 decompresses content based on the Content-Encoding header in chunks to efficiently handle large responses. However, for redirect responses, urllib3 decompresses the entire response body immediately to drain the connection, ignoring read limits and enabling decompression bombs. This flaw can be exploited by malicious servers to cause high CPU usage and large memory allocations on the client side. Applications using icloudpd versions >=1.17.3 and <1.33.0 that rely on urllib3 2.6.2 or earlier and do not disable redirects are affected. The issue is resolved in icloudpd 1.33.0, which upgrades urllib3 to a version that avoids decompressing redirect response content when preload_content=False.

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What to do

Affected software

Description

AI analysisMachine-generated, updated 9 Nov 2026, 19:47 UTC

Technical details

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