{"cve":"CVE-2022-49340","nvd":{"published":"2025-02-26T07:01:10.753","modified":"2026-08-04T10:17:45.080","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nip_gre: test csum_start instead of transport header\n\nGRE with TUNNEL_CSUM will apply local checksum offload on\nCHECKSUM_PARTIAL packets.\n\nipgre_xmit must validate csum_start after an optional skb_pull,\nelse lco_csum may trigger an overflow. The original check was\n\n\tif (csum && skb_checksum_start(skb) < skb->data)\n\t\treturn -EINVAL;\n\nThis had false positives when skb_checksum_start is undefined:\nwhen ip_summed is not CHECKSUM_PARTIAL. A discussed refinement\nwas straightforward\n\n\tif (csum && skb->ip_summed == CHECKSUM_PARTIAL &&\n\t    skb_checksum_start(skb) < skb->data)\n\t\treturn -EINVAL;\n\nBut was eventually revised more thoroughly:\n- restrict the check to the only branch where needed, in an\n  uncommon GRE path that uses header_ops and calls skb_pull.\n- test skb_transport_header, which is set along with csum_start\n  in skb_partial_csum_set in the normal header_ops datapath.\n\nTurns out skbs can arrive in this branch without the transport\nheader set, e.g., through BPF redirection.\n\nRevise the check back to check csum_start directly, and only if\nCHECKSUM_PARTIAL. Do leave the check in the updated location.\nCheck field regardless of whether TUNNEL_CSUM is configured.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":[],"references":["https://git.kernel.org/stable/c/0c92d813c7c9ca2212ecd879232e7d87362fce98","https://git.kernel.org/stable/c/0ffa268724656633af5f37a38c212326d98ebe8c","https://git.kernel.org/stable/c/3d08bc3a5d9b2106f5c8bcf1adb73147824aa006","https://git.kernel.org/stable/c/7596bd7920985f7fc8579a92e48bc53ce4475b21","https://git.kernel.org/stable/c/8d21e9963bec1aad2280cdd034c8993033ef2948"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T21:59:48.811064707+00:00"},"epss":{"cve":"CVE-2022-49340","score":0.00281,"percentile":0.20671,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}