VulnerabilityPublished 27 Oct 2026

CVE-2026-117503: a2aproject a2a-go · Resource Consumption

Affects a2aproject a2a-goSource CVE Database V5

Not known to be exploited · CVSS 6.9 Medium.

Data as of 27 Oct 2026, 14:12 UTC

CVSS 4.0 base score

6.9Medium

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

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, 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: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system 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 Vulnerable System 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 Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 27 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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
a2aprojecta2a-go	Affected 2.0 – 2.4.0 5 affected builds	Fixed in–
GitHuba2aproject/a2a-go`pkg:github/a2aproject/a2a-go`Other threats	Affected 2.0 – 2.4.0 5 affected builds	Fixed in–

CPE configurations (1)

cpe:2.3:a:a2aproject:a2a-go:*:*:*:*:*:*:*:*

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AI-suggested

Upgrade the affected a2aproject a2a-go software to version 2.5.0 or later, which contains the official fix for this resource consumption vulnerability. No other mitigations are specified or required.

Description

CVE-2026-117503 is a resource consumption vulnerability in the a2aproject a2a-go software affecting versions 2.0 through 2.4.0. The flaw exists in an unknown function within the REST SSE handler component (a2asrv/rest.go). This vulnerability can be exploited remotely to cause excessive resource usage. Upgrading to version 2.5.0 addresses the issue.

Impact

The vulnerability enables remote attackers to cause resource consumption, which may degrade or disrupt service availability. There is no indication of privilege escalation, data compromise, or other impacts beyond resource exhaustion. No known exploits are reported in the wild.

Summary

This vulnerability in a2aproject a2a-go up to version 2.4.0 involves a resource consumption flaw in an unspecified function of the REST SSE handler component (a2asrv/rest.go). The vulnerability allows remote attackers to trigger resource exhaustion, potentially impacting service availability. The issue is resolved by upgrading to version 2.5.0, where a patch identified by commit ff6035bd21e44bb3ee1bfa547885b8c08327fa01 has been applied.

References

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