CVE-2026-66392VulnerabilityPublished 21 Oct 2026Updated 30 Oct 2026

Apache bRPC versions before 1.18.0 validate the server certificate chain when client TLS peer verification is enabled

Source GCVE Database

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Authoritative record:CVE-2026-66392· Medium 5.9

Not known to be exploited · CVSS 5.9 Medium : upgrade to 1.18.0 when convenient.

Data as of 30 Oct 2026, 21:05 UTC

CVSS 3.1 base score

5.9Medium

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

Thin evidence

One scorer or none

CVSS scores by source
CISA-ADP	CVSS 3.1	5.9

EPSS: 0.1% chance of exploitation in 30 days – higher than 0% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.18.0

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

Attack Vector: Network
Attack Complexity: High
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: High
Availability: None

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: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 21 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.

ghsa-qv5c-vj5j-fg9q

What to do

Upgrade Apache bRPC and apache/brpc to 1.18.0.

Affected software

Product	Affected	Fixed in
Apache bRPCapache/brpc	Affected <1.18.0	Fixed in 1.18.0
GitHubapache/brpc`pkg:github/apache/brpc`Other threats	Affected <1.18.0	Fixed in 1.18.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade Apache bRPC to version 1.18.0 or later, which includes hostname verification during TLS peer verification. Ensure VERIFY_PEER is enabled with a positive verify_depth. For cases where the certificate identity differs from the URL host, explicitly set VerifyOptions::expected_peer_name. Alternatively, apply the patch available at https://github.com/apache/brpc/pull/3408. Do not disable peer verification while setting expected peer names, as such configurations are rejected.

Description

Apache bRPC versions prior to 1.18.0 perform server certificate chain validation when client TLS peer verification is enabled but do not verify that the certificate matches the expected DNS name or IP address. This allows a network attacker who can intercept or redirect connections and has a certificate issued by a trusted CA for a different name to impersonate the intended TLS endpoint. The issue affects applications using bRPC client Channels connecting over untrusted networks with certificate verification enabled. The vulnerability is addressed by upgrading to version 1.18.0, which adds hostname verification during the TLS handshake.

Impact

An attacker capable of intercepting or redirecting network connections can impersonate the intended TLS server endpoint if they possess a certificate issued by a trusted CA for a different name. This undermines the integrity of TLS connections, potentially allowing man-in-the-middle attacks that can alter or inject malicious data. The vulnerability does not affect confidentiality directly but impacts the integrity of communications.

Summary

Apache bRPC before version 1.18.0 validates the server certificate chain during TLS peer verification but lacks binding of the certificate to the expected DNS name or IP address. This flaw permits a man-in-the-middle attacker with a valid certificate for a different identity, trusted by the client, to impersonate the legitimate TLS endpoint. The vulnerability arises in scenarios where applications connect to untrusted networks with peer verification enabled and trust a CA that can issue certificates for multiple identities. The fix in version 1.18.0 introduces DNS Subject Alternative Name (SAN) or IP SAN verification during the TLS handshake, ensuring the certificate matches the expected endpoint identity. Users can also explicitly set the expected peer name if it differs from the URL host. The patch is also available via a GitHub pull request. Configurations that specify an expected peer name while peer verification is disabled are rejected.

CWE-297Improper Validation of Certificate with Host Mismatch (opens in a new tab)
Variant weaknessLikelihood of exploit: HighOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
The product communicates with a host that provides a certificate, but the product does not properly ensure that the certificate is actually associated with that host.
Architecture and Design
In order to ensure data integrity, the certificate must be valid, and it must pertain to the site that is being accessed.Fully check the hostname of the certificate and provide the user with adequate information about the nature of the problem and how to proceed.
Implementation
If certificate pinning is being used, ensure that all relevant properties of the certificate are fully validated before the certificate is pinned, including the hostname.
Implementation
Be careful of other weaknesses in the code that checks the hostname, since it is still possible to incorrectly check the hostname. For example, attackers could create a certificate with a name that begins with a trusted name followed by a NUL byte, which could cause some string-based comparisons to only examine the…
OWASP Cheat Sheets
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V1.14.1 (opens in a new tab)
V2.8.5 (opens in a new tab)
V2.8.4 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 30 Oct 2026, 21:05 UTC

WeaknessesCWE-297

Technical details

References

Community reviews

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