VulnerabilityPublished 31 Oct 2026

CVE-2026-119197: Awscli@1 · pyasn1 has quadratic-complexity denial of service in binary REAL decoding

Affects awscli@1Source GCVE Database

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Authoritative record:CVE-2026-119197· High 7.5

Not known to be exploited · CVSS 7.5 High · fixed in 0.6.5 : patch awscli@1 soon.

Data as of 31 Oct 2026, 16:22 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

Patch: Available – fixed in 0.6.5

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
Homebrewawscli@1`pkg:brew/awscli%401`Other threats	Affected >=1.20.20	Fixed in–

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AI-suggested

Upgrade pyasn1 to version 0.6.5 or later, where the decoding inefficiency is fixed. Until upgrading, applications should reject or strictly limit ASN.1 input containing REAL values, especially those with large mantissas, before passing data to pyasn1 decoders. The fix in 0.6.5 addresses the issue for BER, CER, and DER decoders. No other mitigations are specifically recommended.

Description

CVE-2026-119197 is a denial of service vulnerability in pyasn1 versions 0.6.4 and earlier, affecting the decoding of binary ASN.1 REAL values with large mantissas. The decoding process has quadratic time complexity due to inefficient byte processing, causing excessive CPU consumption. This impacts BER, CER, and DER decoders using the vulnerable RealPayloadDecoder. The vulnerability can be triggered when an application decodes attacker-controlled ASN.1 data containing REAL values. The issue was fixed in pyasn1 version 0.6.5 by optimizing the decoding loop.

Impact

The vulnerability allows an attacker who can supply ASN.1 data containing REAL values to cause high CPU consumption during decoding, potentially leading to denial of service by exhausting a CPU core. The attack requires the ability to influence input passed to the pyasn1 decoder and is limited by application-level input restrictions. There is no direct impact on confidentiality or integrity, and no evidence of remote exploitation without application-level access. The vulnerability affects availability by causing CPU exhaustion during decoding of crafted ASN.1 REAL values.

Summary

In pyasn1 versions up to 0.6.4, decoding a binary-encoded ASN.1 REAL with a large mantissa causes CPU time to grow quadratically with mantissa length. This is due to a loop that shifts and slices the mantissa one octet at a time, resulting in inefficient processing. The vulnerability affects BER, CER, and DER decoders that use the shared RealPayloadDecoder. An attacker can cause CPU exhaustion by supplying ASN.1 data with large REAL values to an application that decodes such data without strict input limits. The flaw was fixed in pyasn1 0.6.5 by replacing the loop with a single int.from_bytes conversion, preserving decoding correctness while eliminating the quadratic complexity.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 31 Oct 2026, 16:22 UTC

Technical details

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