VulnerabilityPublished 13 Aug 2026Updated 29 Oct 2026

CVE-2026-48524: Hermes agent · PyJWKClient unbounded JWKS endpoint requests via attacker-controlled kid values (DoS)

Affects hermes-agentSource GCVE Database

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Authoritative record:CVE-2026-48524· Low 3.7

Not known to be exploited · CVSS 3.7 Low : upgrade to 2026.7.1 when convenient.

Data as of 30 Oct 2026, 09:02 UTC

CVSS 3.1 base score

3.7Low

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

Patch: Available – fixed in 2026.7.1

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

Attack Vector: Network
Attack Complexity: High
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: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
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 28 May 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 29 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 hermes-agent to 2026.7.1.

Affected software

Product	Affected	Fixed in
Homebrewhermes-agent`pkg:brew/hermes-agent`Other threats	Affected >=2026.4.30 <2026.7.1	Fixed in 2026.7.1

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 in Hermes agent version 2026.7.1 that addresses this issue by adding a refresh cooldown to limit JWKS endpoint requests and changing cache handling to prevent clearing valid data on network errors. Users should upgrade to version 2026.7.1 or later to remediate this vulnerability. No additional mitigation actions are required beyond applying the official fix.

Description

CVE-2026-48524 is a denial-of-service vulnerability in Hermes agent's PyJWKClient component. The flaw causes the client to issue a fresh HTTP request to the JWKS endpoint for every JWT with an unknown key ID (kid) without rate limiting. This can be exploited by an attacker sending tokens with attacker-controlled kid values, triggering unlimited outbound requests and causing network latency and potential cascading failures in authentication. The vulnerability affects versions from 2026.4.30 up to but not including 2026.7.1. A fix is available in version 2026.7.1.

Impact

The vulnerability enables denial of service against the JWKS endpoint due to unlimited requests triggered by attacker-controlled kid values. It also causes denial of service against the application through increased network I/O latency. Furthermore, cascading failures may occur if rate limiting on the JWKS endpoint clears the cache, disrupting legitimate authentication processes. However, the impact is limited to reduced authentication availability rather than full service denial.

Summary

The vulnerability arises because PyJWKClient.get_signing_key() forcibly refreshes the JWKS cache on every unknown kid value by calling get_signing_keys(refresh=True), bypassing the TTL cache and lacking any cooldown or rate limiting. Additionally, on network errors, the JWKS cache is cleared due to a finally block writing None to the cache, which can exacerbate the issue by removing valid cached keys. An attacker can exploit this by sending JWTs with arbitrary kid values to cause unbounded requests to the JWKS endpoint, leading to denial of service against the JWKS endpoint and increased latency in the application. The impact is limited to reduced authentication availability until the next successful JWKS fetch, not a complete denial of service. The suggested fix involves adding a refresh cooldown to prevent repeated refreshes within the TTL period and modifying cache handling to avoid clearing valid data on errors.

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Affected software

Description

AI analysisMachine-generated, updated 30 Oct 2026, 09:02 UTC

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