CVE-2026-119195VulnerabilityPublished 31 Oct 2026

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

Affects hermes-agentSource GCVE Database

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Authoritative record:CVE-2026-119195· High 7.5

Not known to be exploited · CVSS 7.5 High · fixed in 2026.4.30 : patch hermes-agent soon.

Data as of 31 Oct 2026, 18:23 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 2026.4.30

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
Homebrewhermes-agent`pkg:brew/hermes-agent`Other threats	Affected >=0.21.6 >=2026.9.14 <=2026.9.24	Fixed in–

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AI-suggested

A patch is available in hermes-agent version 2026.4.30 that fixes this vulnerability. Users should upgrade to this version or later to remediate the issue. Until patched, applications should implement input validation or resource limits on ASN.1 decoding to mitigate potential CPU exhaustion. No other vendor advisory states that no action is required or that the issue is already mitigated.

Description

In pyasn1 versions 0.6.4 and earlier used by hermes-agent, a quadratic-time denial of service vulnerability exists in the decoding of constructed OCTET STRINGs, constructed character strings, and indefinite-length ANY types. This flaw causes CPU usage to grow quadratically with the number of fragments during ASN.1 decoding, potentially allowing an attacker to exhaust CPU resources by supplying crafted ASN.1 input. The vulnerability affects BER and CER decoding paths and certain non-conforming DER inputs when an asn1Spec is used. No confidentiality or integrity impact is reported. A fix is available in version 2026.4.30.

Impact

An attacker who can supply crafted ASN.1 input to an affected pyasn1 decoder can cause excessive CPU consumption due to quadratic-time string reassembly during decoding. This can lead to denial of service by exhausting CPU resources on the decoding worker. There is no impact on confidentiality or integrity. The vulnerability requires the application to decode attacker-controlled ASN.1 data without adequate input validation or resource limits. The vulnerability affects BER and CER decoding and certain non-DER inputs when using asn1Spec. No known exploits in the wild have been reported.

Summary

The vulnerability in pyasn1 0.6.4 and earlier arises from inefficient string reassembly in the BER and CER decoders when processing constructed OCTET STRINGs, constructed character strings, and indefinite-length ANY types. The decoder concatenates fragments using repeated string concatenation operations that copy increasingly large prefixes, resulting in O(N²) CPU time relative to the number of fragments. This can be triggered by valid BER and conforming CER inputs, as well as certain non-DER-compliant inputs accepted by the DER decoder when an asn1Spec is specified. The issue does not affect confidentiality or integrity but can cause CPU exhaustion in applications that decode attacker-controlled ASN.1 data without input or resource limits. The vulnerability is distinct from a previous OID-related issue fixed in 0.6.4. The affected hermes-agent versions are >=0.21.6 and <2026.4.30, and >=2026.9.14. The fix is included in version 2026.4.30.

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What to do

Affected software

Description

AI analysisMachine-generated, updated 31 Oct 2026, 17:06 UTC

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