VulnerabilityPublished 13 Aug 2026Updated 29 Oct 2026

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

Affects lexiconSource GCVE Database

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Not known to be exploited · CVSS 7.5 High : upgrade to 3.25.2_2 soon.

Data as of 30 Oct 2026, 07:31 UTC

CVSS 3.1 base score

7.5High

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

Patch: Available – fixed in 3.25.2_2

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 lexicon to 3.25.2_2.

Affected software

Product	Affected	Fixed in
Homebrewlexicon`pkg:brew/lexicon`Other threats	Affected >=3.11.2 <3.25.2_2	Fixed in 3.25.2_2

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 3.25.2_2 that addresses this vulnerability. Users should upgrade to this fixed version or later to prevent memory exhaustion attacks. Until patched, avoid passing untrusted or excessively large comma-separated selector lists to soupsieve.compile() or Beautiful Soup's .select()/.select_one().

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 with many comma-separated items, causing the parser to allocate excessive heap memory, leading to denial of service. This affects applications that use soupsieve.compile() or Beautiful Soup's .select()/.select_one() with user-supplied selectors. The issue is fixed in version 3.25.2_2.

Impact

An attacker can cause denial of service by exhausting memory on servers running affected versions of soupsieve or Beautiful Soup 4 that compile user-supplied CSS selectors. This can result in out-of-memory kills in containerized environments, swap thrashing on physical servers, or process termination due to Python MemoryError exceptions. No authentication or user interaction is required, and the attack scales linearly with the number of selectors supplied. Multiple concurrent requests can amplify the impact.

Summary

The CSS selector parser in soupsieve allocates memory linearly proportional to the number of comma-separated selectors without enforcing any limit. Each selector object consumes approximately 976 bytes of heap memory, causing a high amplification ratio (~488x) between input size and memory allocated. For example, a 500 KB selector string with 250,000 items can cause allocation of about 244 MB of memory. This can lead to memory exhaustion and denial of service in server-side Python applications that accept user-supplied CSS selectors. The vulnerability affects soupsieve versions >=3.11.2 and <3.25.2_2 and is fixed in 3.25.2_2.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 30 Oct 2026, 07:31 UTC

Technical details

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