CVE-2026-119195VulnerabilityPublished 31 Oct 2026

Aws shell: pyasn1 has quadratic-time denial of service in constructed string and indefinite-length ANY decoding

Affects aws-shellSource GCVE Database

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Mentioned vulnerabilities

CVE-2026-59885

Authoritative record:CVE-2026-119195· High 7.5

Not known to be exploited · CVSS 7.5 High.

Data as of 31 Oct 2026, 17:21 UTC

CVSS 3.1 base score

7.5High

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

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	7.5

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 29 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

Affected software

Product	Affected	Fixed in
Homebrewaws-shell`pkg:brew/aws-shell`Other threats	Affected >=0.1.0	Fixed in–

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AI-suggested

Until a fix is available, applications should implement input validation or resource limits on ASN.1 decoding to mitigate CPU exhaustion risks. Avoid decoding untrusted ASN.1 inputs without such controls.

Description

A denial of service vulnerability exists in pyasn1 version 0.6.4 and earlier used by aws-shell, where decoding certain constructed ASN.1 string types or indefinite-length ANY types can cause quadratic CPU time consumption. This occurs due to inefficient string concatenation in the decoder, leading to CPU exhaustion when processing attacker-controlled inputs. The vulnerability affects BER and CER decoding paths and certain non-conforming DER inputs. No confidentiality or integrity impact is reported. The CVSS v3.1 base score is 7.5 (high severity).

Impact

An attacker who can supply crafted ASN.1 input to an application using the affected pyasn1 decoder can cause excessive CPU consumption leading to denial of service. The attack requires no privileges or user interaction and can be triggered by valid BER and conforming CER inputs. No confidentiality or integrity impacts are known. The vulnerability could allow exhaustion of decoding workers and degrade service availability.

Summary

In pyasn1 versions 0.6.4 and earlier, the BER and CER decoders for constructed OCTET STRINGs and character strings, as well as indefinite-length ANY types, perform repeated concatenations of fragments using inefficient string operations. This causes the CPU time to grow roughly quadratically with the number of fragments, despite linear growth in input size. The issue affects multiple ASN.1 string types inheriting the same decoder path. The DER decoder rejects constructed OCTET STRINGs by default but accepts certain non-DER constructed strings when an asn1Spec is provided, exposing the same vulnerability. The vulnerability can be triggered by attacker-controlled ASN.1 inputs, potentially exhausting CPU resources and causing denial of service. The vulnerability is distinct from a previously fixed OID-related issue (CVE-2026-59885) and remains unpatched in pyasn1 0.6.4.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 31 Oct 2026, 17:21 UTC

Technical details

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