VulnerabilityPublished 13 Aug 2026Updated 31 Oct 2026

CVE-2026-23490: Gcalcli · pyasn1 has a DoS vulnerability in decoder

Affects gcalcliSource GCVE Database

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Not known to be exploited · CVSS 7.5 High : upgrade to 4.5.1_7 soon.

Data as of 1 Nov 2026, 01:38 UTC

CVSS 3.1 base score

7.5High

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

Patch: Available – fixed in 4.5.1_7

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 31 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 gcalcli to 4.5.1_7.

Patches and advisories

Affected software

Product	Affected	Fixed in
Homebrewgcalcli`pkg:brew/gcalcli`Other threats	Affected >=4.5.0 <4.5.1_7	Fixed in 4.5.1_7

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 to update pyasn1 to the fixed version 4.5.1_7 or later. The vendor advisory from Red Hat confirms the availability of an official fix. Users should upgrade to the patched version to prevent denial-of-service conditions caused by malformed RELATIVE-OID values. No additional mitigation steps are indicated by the vendor advisory.

Description

A denial-of-service (DoS) vulnerability exists in pyasn1 version 0.6.1 used by gcalcli, caused by memory exhaustion from malformed RELATIVE-OID values with excessive continuation octets during decoding. This flaw can cause affected applications to hang or crash due to resource exhaustion. The vulnerability affects versions >=4.5.0 and <4.5.1_7 of gcalcli. A fix is available in version 4.5.1_7. The issue may impact systems that decode ASN.1 data such as LDAP servers, TLS/SSL endpoints, and OCSP responders.

Impact

This vulnerability can cause affected applications to consume excessive memory and hang or crash when decoding maliciously crafted ASN.1 RELATIVE-OID values. The impact is denial of service, potentially disrupting services such as LDAP servers, TLS/SSL endpoints, and OCSP responders that rely on pyasn1 for ASN.1 decoding. There is no confidentiality or integrity impact reported. No known exploits in the wild have been reported.

Summary

The pyasn1 library version 0.6.1 contains a denial-of-service vulnerability (CVE-2026-23490) in its BER decoder. The flaw arises from improper handling of malformed RELATIVE-OID values containing excessive continuation octets, which causes the decoder to perform excessive bit-shifting operations leading to memory exhaustion. A proof-of-concept demonstrates that crafted ASN.1 packets with large sequences of continuation bytes can cause the decoder to consume large amounts of memory and potentially crash. This vulnerability affects gcalcli versions >=4.5.0 and <4.5.1_7, which depend on pyasn1. Red Hat has issued an advisory and released patches to address this issue in their python-pyasn1 packages. The CVSS v3.1 base score is 7.5 (high severity) with no confidentiality or integrity impact but high availability impact due to denial of service.

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