GoBGP: Remote Denial of Service (Panic) via Malformed Well-known Path Attribute

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

GoBGP is an open source Border Gateway Protocol (BGP) implementation in the Go Programming Language. In version 4.3.0, a remote Denial of Service (DoS) vulnerability exists in GoBGP due to a nil pointer dereference. When a malformed BGP UPDATE message contains an unrecognized Path Attribute marked as "Well-known," the daemon fails to interrupt the message handling flow. This results in an illegal memory access and a full process crash (panic). This issue has been patched in version 4.4.0.

Source published

7 May 2026 11:50:41 UTC

Source modified

7 May 2026 12:34:38 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

GoBGP is an open source Border Gateway Protocol (BGP) implementation in the Go Programming Language. In version 4.3.0, a remote Denial of Service (DoS) vulnerability exists in GoBGP due to a nil pointer dereference. When a malformed BGP UPDATE message contains an unrecognized Path Attribute marked as "Well-known," the daemon fails to interrupt the message handling flow. This results in an illegal memory access and a full process crash (panic). This issue has been patched in version 4.4.0.

Source published

May 7, 2026, 11:50:41 AM (timezone not stated)

Source modified

May 7, 2026, 12:34:38 PM (timezone not stated)

Observed here

1 Nov 2026 07:10:16 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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EUVD CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

GoBGP is an open source Border Gateway Protocol (BGP) implementation in the Go Programming Language. In version 4.3.0, a remote Denial of Service (DoS) vulnerability exists in GoBGP due to a nil pointer dereference. When a malformed BGP UPDATE message contains an unrecognized Path Attribute marked as "Well-known," the daemon fails to interrupt the message handling flow. This results in an illegal memory access and a full process crash (panic). This issue has been patched in version 4.4.0.

Source published

7 May 2026 12:16:17 UTC

Source modified

26 Oct 2026 22:10:00 UTC

Observed here

27 Oct 2026 10:10:19 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

### Summary A remote Denial of Service (DoS) vulnerability exists in GoBGP due to a nil pointer dereference. When a malformed BGP UPDATE message contains an unrecognized Path Attribute marked as "Well-known," the daemon fails to interrupt the message handling flow. This results in an illegal memory access and a full process crash (panic). ### Details The vulnerability is located in the Finite State Machine (FSM) message handling loop in pkg/server/fsm.go. According to RFC 4271, any Path Attribute with the Optional bit set to 0 is treated as "Well-known." If the Type Code is unrecognized, the BGP speaker MUST send a NOTIFICATION message. In GoBGP v4.3.0, when such an attribute (e.g., Type 0xEE or 0xFF with flags 0x40) is received, the parsing layer identifies the error. However, the logic in recvMessageloop (around Line 1826) does not properly halt execution. It proceeds to reference the body of the parsed message. Because the message was deemed invalid during the initial attribute check, the body pointer is nil, leading to: panic: runtime error: invalid memory address or nil pointer dereference. This bypasses the intended error-handling mechanism and causes the entire BGP daemon to terminate, rather than just closing the affected session. ``` panic: runtime error: invalid memory address or nil pointer dereference [signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0xc225e4] goroutine 50 [running]: github.com/osrg/gobgp/v4/pkg/server.(*fsmHandler).recvMessageloop(0x19f29bca92c0, {0x10069f0, 0x19f29bc48780}, {0x1014658, 0x19f29bc2a890}, 0x19f29baa0540, 0x19f29bc393b0, 0x19f29bc96cc0?) /home/base/Desktop/gobgp/pkg/server/fsm.go:1826 +0xa44 created by github.com/osrg/gobgp/v4/pkg/server.(*fsmHandler).established in goroutine 37 /home/base/Desktop/gobgp/pkg/server/fsm.go:1916 +0x2d5 exit status 2 ``` ### PoC GoBGP Version: v4.3.0 Configure GoBGP with a neighbor (e.g., 192.168.31.195) in passive mode. Establish a standard BGP session (OPEN/KEEPALIVE exchange). Send a specifically crafted UPDATE packet containing an unrecognized Type Code marked as "Well-known" (Optional bit = 0). Payload 1 (Hex): ``` FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF 00 17 # Length: 23 02 # Type: UPDATE 00 00 # Withdrawn Routes Length: 0 00 04 # Total Path Attribute Length: 4 40 EE 00 # Flag: 0x40 (Well-known, Transitive), Type: 0xEE (Unknown), Len: 0 ``` Payload 2 (Hex): ``` FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF 00 17 # Length: 23 02 # Type: UPDATE 00 00 # Withdrawn Routes Length: 0 00 04 # Total Path Attribute Length: 4 40 01 01 00 # IGP Attribute 40 FF 00 # Flag: 0x40 (Well-known, Transitive), Type: 0xFF (Unknown), Len: 0 ``` ### Impact This vulnerability affects all GoBGP deployments peering with external or internal speakers. A single malformed UPDATE message from any peer can trigger a nil pointer dereference, causing the GoBGP daemon to panic and crash.

Source published

29 Apr 2026 20:43:36 UTC

Source modified

24 Jul 2026 19:11:42 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Publisher rating · HIGH

GoBGP: Remote Denial of Service (Panic) via Malformed Well-known Path Attribute in github.com/osrg/gobgp

Source published

24 Jul 2026 18:35:55 UTC

Source modified

24 Jul 2026 19:00:21 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.