VulnerabilityPublished 6 Oct 2026Updated 30 Oct 2026

CVE-2026-104874: Reference leak in CIMultiDict/MultiDict items-view union and subtraction

Affects checkovSource GCVE Database

Compare

Authoritative record:CVE-2026-104874· Medium 5.3

Not known to be exploited · CVSS 5.3 Medium : upgrade to 3.3.20 when convenient.

Data as of 30 Oct 2026, 20:25 UTC

CVSS 3.1 base score

5.3Medium

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 38% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.3.20

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

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

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: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 2 Oct 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 30 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 checkov to 3.3.20.

Affected software

Product	Affected	Fixed in
Homebrewcheckov`pkg:brew/checkov`Other threats	Affected >=3.2.470 <3.3.20	Fixed in 3.3.20

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 and should be applied. The issue is fixed in version 3.3.20 of the affected product. Users should upgrade to this version or later to remediate the memory leak. No other mitigation or workaround is indicated.

Description

A reference leak vulnerability exists in the items-view union and subtraction operators of aio-libs/multidict versions 6.7.0 through 6.9.0. This flaw allows a remote client to cause unbounded memory growth by leaking key-identity and value objects during certain set operations on dictionary views. The leak occurs because new references are created but not properly released in specific code paths. This issue can cause server processes using these versions to consume increasing amounts of memory until termination.

Impact

The vulnerability causes a denial-of-service condition through memory exhaustion. Remote clients controlling HTTP headers or query strings can trigger unbounded memory growth on servers using the affected multidict versions, potentially leading to process termination due to out-of-memory conditions. There is no impact on confidentiality or integrity, only availability is affected.

Summary

The vulnerability is a reference leak in the C extension of aio-libs/multidict affecting versions 6.7.0 through 6.9.0. The leak occurs in the items-view union (`operand | d.items()`) and subtraction (`d.items() - operand`) operators, where each element leaks one key-identity object and one value object due to missing decref calls on new references returned by `_multidict_itemsview_parse_item()`. This leads to unreclaimable memory growth as the leaked references accumulate. The root cause is a behavioral regression introduced between versions 6.6.4 and 6.7.0 related to ownership changes in `md_calc_identity()`. The leak is demonstrated by proof-of-concept code showing increased reference counts and growing resident memory size under repeated operations. The issue is fixed in version 3.3.20 of the affected product (checkov), which includes the multidict dependency.

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 30 Oct 2026, 18:06 UTC

Technical details

References

Community reviews

Related threats