frr: bgpd double free of peer-group Site-of-Origin when dynamic neighbors disconnect
Summary
| CVE | CVE-2026-120221 |
|---|---|
| State | PUBLISHED |
| Assigner | NetDEF |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-11-13 12:17:03 UTC |
| Updated | 2026-11-14 15:16:58 UTC |
| Description | In FRRouting, bgpd frees the same memory twice when dynamic BGP neighbors disconnect, if the peer-group used by a "bgp listen range" also has a Site-of-Origin configured ("neighbor PG soo"). Each dynamic neighbor shares the peer-group's SoO value instead of getting its own copy, but frees it as its own when the neighbor is deleted, which happens as soon as its connection closes. The first disconnect leaves the peer-group pointing at freed memory, and the second disconnect frees it again, causing bgpd to abort and drop all BGP sessions on the router. Any host whose address falls inside the listen range can trigger this by opening and closing two TCP connections to the BGP port, without sending any BGP message and without knowing the AS number, and can repeat it each time bgpd restarts. If the peer-group has a TCP-MD5 password, only hosts that know the password can trigger it. Two ordinary flaps of legitimate dynamic neighbors have the same effect. Between the two frees, displaying the configuration ("show running-config") or establishing a dynamic neighbor also reads the freed memory, which can crash bgpd after a single disconnect. Only configurations that combine a listen range with a SoO on the same peer-group are affected. |
Risk And Classification
Primary CVSS: v4.0 8.2 HIGH from 57a55968-44ac-464c-a794-6ba3baad09c4
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:N/R:A/V:X/RE:X/U:X
Problem Types: CWE-415 | CWE-416 | CWE-415 CWE-415 Double Free | CWE-416 CWE-416 Use After Free: the peer-group's SoO pointer is left dangling after the first dynamic neighbor is deleted and is read by later neighbors and by the configuration writer
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | 57a55968-44ac-464c-a794-6ba3baad09c4 | Secondary | 8.2 | HIGH | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/C... |
| 4.0 | CNA | CVSS | 8.2 | HIGH | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:N/R:A |
CVSS v4.0 Breakdown
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:N/R:A/V:X/RE:X/U:X
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Frrouting | Frrouting | affected 01da2d26911c72023e71579bf4feeb707087ef50 * git | Not specified |
| CNA | Frrouting | Frrouting | affected 8.4.0 10.2.7 semver | Not specified |
| CNA | Frrouting | Frrouting | affected 10.3.0 10.3.5 semver | Not specified |
| CNA | Frrouting | Frrouting | affected 10.4.0 10.4.6 semver | Not specified |
| CNA | Frrouting | Frrouting | affected 10.5.0 10.5.6 semver | Not specified |
| CNA | Frrouting | Frrouting | affected 10.6.0 10.6.3 semver | Not specified |
| CNA | Frrouting | Frrouting | affected 10.7.0 10.7.2 semver | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/FRRouting/frr/pull/21685/changes/6a96f515760dc278147fbf802777... | 57a55968-44ac-464c-a794-6ba3baad09c4 | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Nageswara Soma <[email protected]> (not reported as security issue) (en)
CNA: Anthropic OSS-scanner (re-report, ANT-2026-X4QI9LP4) (en)
Additional Advisory Data
Workarounds
CNA: Do not configure "neighbor <peer-group> soo" on a peer-group used by "bgp listen range". Instead, set the SoO extended community with an inbound route-map, or set "neighbor soo" on statically configured neighbors. Configuring a TCP-MD5 "password" on the peer-group limits the trigger to hosts that know the key.