VulnerabilityPublished 13 Aug 2026Updated 29 Oct 2026

CVE-2026-49476: Mcp atlassian · Soup Sieve has Memory Exhaustion via Large Comma-Separated Selector Lists

Affects mcp-atlassianSource GCVE Database

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Not known to be exploited · CVSS 7.5 High : upgrade to 0.21.1_8 soon.

Data as of 30 Oct 2026, 08:16 UTC

CVSS 3.1 base score

7.5High

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

Patch: Available – fixed in 0.21.1_8

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 29 Oct 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 mcp-atlassian to 0.21.1_8.

Affected software

Product	Affected	Fixed in
Homebrewmcp-atlassian`pkg:brew/mcp-atlassian`Other threats	Affected >=0.11.9 <0.21.1_8	Fixed in 0.21.1_8

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

AI-suggested

A patch is available in soupsieve version 0.21.1_8 that addresses this vulnerability. Users should upgrade to version 0.21.1_8 or later to mitigate the risk. No other specific mitigations are indicated by the vendor advisory. Applications should avoid passing untrusted, large comma-separated selector lists to soupsieve.compile() or Beautiful Soup's selector methods until patched.

Description

A memory exhaustion vulnerability exists in soupsieve, the CSS selector engine used by Beautiful Soup 4, due to unbounded memory allocation when compiling large comma-separated selector lists. An attacker can supply a crafted CSS selector string to soupsieve.compile() or Beautiful Soup's .select()/.select_one() methods, causing the application to allocate hundreds of megabytes of heap memory from a relatively small input, leading to denial of service via memory exhaustion. This affects versions >=0.11.9 and <0.21.1_8 of soupsieve. A fix is available in version 0.21.1_8.

Impact

An attacker can cause denial of service by exhausting available memory on servers running vulnerable versions of soupsieve. This can result in out-of-memory kills in containerized environments, swap thrashing on physical servers, or process termination via Python's MemoryError exception. The attack scales linearly with the number of selectors and can be tuned to exhaust memory limits precisely. Multiple concurrent requests can amplify the effect. The vulnerability affects any application that accepts user-supplied CSS selectors and uses soupsieve or Beautiful Soup for parsing, including widely used web scraping APIs and content filtering tools.

Summary

The CSS selector parser in soupsieve allocates memory linearly proportional to the number of comma-separated selectors in the input string, without enforcing limits. Each selector object consumes approximately 976 bytes of heap memory. A crafted selector string with 250,000 comma-separated items (e.g., 'a,a,a,...') of about 500 KB input size can cause allocation of approximately 244 MB of heap memory, an amplification ratio of about 488x. This can lead to memory exhaustion and denial of service in any Python application that compiles user-supplied CSS selectors via soupsieve or Beautiful Soup's selector methods. The vulnerability affects soupsieve versions >=0.11.9 and <0.21.1_8. The issue was responsibly disclosed and independently validated by researchers from the University of Sydney. No authentication or user interaction is required to exploit this vulnerability.

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Description

AI analysisMachine-generated, updated 30 Oct 2026, 08:16 UTC

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