How should we interpret CVSS severity scores?

CVSS estimates technical severity, but it does not automatically equal business risk. Prioritize using context like internet exposure, asset criticality, known exploitation, and whether compensating controls exist. A Medium CVSS on an exposed production system can be more urgent than a Critical on an isolated non-production host.

Vulnerability Database

Q: What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

Q: What's the difference between a vulnerability, an exploit, and a zero-day?

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. Risk increases sharply when exploitation becomes reliable or widespread.

Q: Why do vulnerabilities keep reappearing in our environment?

Recurring findings usually come from incomplete asset discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host.

Q: How do we prioritize remediation without burning out the team?

Use a repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress so remediation is steady, not reactive.

Q: How can SynScan help reduce vulnerability risk over time?

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361,925

Total vulnerabilities in the database

CVE-2026-49838 — github.com/osrg/gobgp/v4

Improper Validation of Array Index

Found through variant analysis based on CVE-2026-41643

Summary

GoBGP accepts a zero-length AS_PATH during UPDATE decoding and later panics while validating that attribute for a confederation eBGP peer. The vulnerable path is in the BGP UPDATE validator: a malformed UPDATE that should be rejected as a malformed AS_PATH instead reaches an unchecked p.Value[0] access, allowing a configured confederation eBGP peer to trigger a denial of service.

Affected

Project: gobgp
Repo: https://github.com/osrg/gobgp
Pinned ref: c24629411ba49f160d9dc09126f418218127e016

Root cause

An established peer's receive path reads BGP bytes from the network connection in pkg/server/fsm.go:1267, parses UPDATE bodies through the BGP message decoder, and validates decoded UPDATEs with peer state at pkg/server/fsm.go:1849. The UPDATE decoder walks the path-attribute list in pkg/packet/bgp/bgp.go:15773 and selects the concrete attribute parser from the attacker-controlled attribute type at pkg/packet/bgp/bgp.go:15855. For AS_PATH, PathAttributeAsPath.DecodeFromBytes returns nil when the decoded attribute length is zero (pkg/packet/bgp/bgp.go:11533, pkg/packet/bgp/bgp.go:11538), leaving p.Value empty rather than reporting a malformed attribute. Validation then dispatches each decoded attribute through ValidateAttribute (pkg/packet/bgp/validate.go:34); in the confederation eBGP branch, pkg/packet/bgp/validate.go:162 indexes p.Value[0] before checking that any AS_PATH segment was decoded. The eBGP and confederation guards are normal peer-state gates: pkg/config/oc/util.go:127 defines eBGP as peer AS differing from local AS, pkg/config/oc/util.go:116 checks confederation membership, and pkg/server/fsm.go:740 and pkg/server/fsm.go:741 copy those results into the FSM state used by the validator.

Reproduction

INT-bgp-gobgp-confed-empty-aspath-panic.zip

bash ./poc/run.sh

TRIGGERED: confed empty AS_PATH validation panic: runtime error: index out of range

The TRIGGERED line is the recovered panic fingerprint from the confederation eBGP validation path after a zero-length AS_PATH has decoded successfully. A build failure or any output without that fingerprint would not demonstrate this bug, because the signal is tied to the unchecked AS_PATH segment access.

Impact

A remote unauthenticated peer that is configured as a confederation eBGP neighbor can establish a BGP session and send a single malformed UPDATE containing a syntactically valid AS_PATH attribute header with zero value length. Because the decode path does not turn that empty AS_PATH into a MessageError, normal malformed-attribute handling is bypassed and validation panics before GoBGP can return a BGP NOTIFICATION. The demonstrated effect is denial of service for the receive goroutine and peer session, with potential process termination if the panic is not recovered by the runtime path; no memory corruption, data disclosure, authentication bypass, or code execution is claimed.

Suggested fix

diff --git a/pkg/packet/bgp/validate.go b/pkg/packet/bgp/validate.go
index 2237afb..f07f4fa 100644
--- a/pkg/packet/bgp/validate.go
+++ b/pkg/packet/bgp/validate.go
@@ -159,6 +159,9 @@ func ValidateAttribute(a PathAttributeInterface, rfs map[Family]BGPAddPathMode,
 	case *PathAttributeAsPath:
 		if isEBGP {
 			if isConfed {
+				if len(p.Value) == 0 {
+					return false, NewMessageError(eCode, eSubCodeMalformedAspath, nil, &quot;empty AS_PATH for confederation eBGP&quot;)
+				}
 				if segType := p.Value[0].GetType(); segType != BGP_ASPATH_ATTR_TYPE_CONFED_SEQ {
 					return false, NewMessageError(eCode, eSubCodeMalformedAspath, nil, fmt.Sprintf(&quot;segment type is not confederation seq (%d)&quot;, segType))
 				}

Resources

https://github.com/osrg/gobgp/blob/c24629411ba49f160d9dc09126f418218127e016/pkg/packet/bgp/bgp.go#L11533-L11540
https://github.com/osrg/gobgp/blob/c24629411ba49f160d9dc09126f418218127e016/pkg/packet/bgp/validate.go#L159-L164

Published: Jul 9, 2026
Updated: Jul 10, 2026
CVE: CVE-2026-49838
GHSA: GHSA-frrj-87jh-2772
Severity: Medium
Exploit:
CISA KEV:

CVSS v3:

Severity: Medium
Score: 5.9
AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

CWEs:

CWE-129

Affected Software
References

Software	From	Fixed in
github.com/osrg/gobgp/v4	-	4.7.0

https://github.com/osrg/gobgp/security/advisories/GHSA-frrj-87jh-2772

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.