{"api_version":"1","generated_at":"2026-09-25T12:39:46+00:00","cve":"CVE-2026-98158","urls":{"html":"https://cve.report/CVE-2026-98158","api":"https://cve.report/api/cve/CVE-2026-98158.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-98158","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-98158"},"summary":{"title":"ppp_async: drop the errored frame instead of resetting its headroom","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nppp_async: drop the errored frame instead of resetting its headroom\n\nppp_receive_nonmp_frame() prepends a two-byte direction tag before running\nthe pass/active BPF filters:\n\n\t*(__be16 *)skb_push(skb, 2) = htons(PPP_FILTER_INBOUND_TAG);\n\nNothing on the receive path guarantees those two bytes of headroom. The\nframe-error path in ppp_async's process_input_packet() resets a reused skb's\nheadroom to zero while claiming to restore it to a freshly allocated state -\nbut a fresh skb from dev_alloc_skb() carries NET_SKB_PAD:\n\n\terr:\n\t\tif (skb) {\n\t\t\t/* make skb appear as freshly allocated */\n\t\t\tskb_trim(skb, 0);\n\t\t\tskb_reserve(skb, - skb_headroom(skb));\n\t\t}\n\nap->rpkt still points at that skb, so the next frame is reassembled into it\nwith no headroom at all. A peer that sends a bad-FCS frame followed by one\nbeginning ff 03 then leaves a single byte of headroom by the time the filter\ntag is pushed, which lands one byte below skb->head:\n\n  skbuff: skb_under_panic: len:49 put:2 head:ffff888003c10000\n          data:ffff888003c0ffff tail:0x30 end:0x640 dev:<NULL>\n  kernel BUG at net/core/skbuff.c:214!\n  RIP: 0010:skb_panic+0x13e/0x230\n  Call Trace:\n   skb_push+0xbd/0x100\n   ppp_receive_nonmp_frame+0x48a/0x1d10\n   ppp_input+0x4e9/0x2f80\n   ppp_async_process+0x2a/0xe0\n   tasklet_action_common+0x20f/0x8a0\n   handle_softirqs+0x18e/0x590\n  Kernel panic - not syncing: Fatal exception in interrupt\n\nZeroing the headroom violates the NET_SKB_PAD guarantee that dev_alloc_skb()\ngives the rest of the receive path. Besides the filter panic above, when CCP\ncompression is enabled ppp_decompress_frame() hands skb->data - 2 to\n->decompress()/->incomp(), which then reads out of bounds before skb->head\nfor the same reason.\n\nRather than restore the headroom, drop the errored frame - as ppp_synctty\nalready does on its error path - and clear ap->rpkt so the next frame is\nreassembled into a fresh skb with proper headroom. This is simpler and fixes\nboth the filter under-panic and the CCP out-of-bounds read.\n\nThe original V1 of this patch made room in ppp_receive_nonmp_frame() with\nskb_cow_head(); Eric pointed out that fixing the root cause in the transport\nis the right approach.\n\nFound by fuzzing the PPP receive path with a mutating peer on a pty; it is an\ninteresting (remote) DoS: root configures PPP, the peer supplies two crashing\nframes. The reproducer (repro-ppp-skb.c, unchanged from v1) panics in about a\nsecond, and returns cleanly with this applied.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-09-25 11:17:47","updated_at":"2026-09-25 11:17:47"},"problem_types":[],"metrics":[],"references":[{"url":"https://git.kernel.org/stable/c/0c53eb14975f029abd6b26896a460f0d2aaefe6b","name":"https://git.kernel.org/stable/c/0c53eb14975f029abd6b26896a460f0d2aaefe6b","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/717137221c7d90e7c98bda9a370c9da6cbf015e5","name":"https://git.kernel.org/stable/c/717137221c7d90e7c98bda9a370c9da6cbf015e5","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/d0fc3dabfe67caf084e7119ceb2ee23f5ad2f2da","name":"https://git.kernel.org/stable/c/d0fc3dabfe67caf084e7119ceb2ee23f5ad2f2da","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/8dc5d98a16fa23c00999aecf10018c9f69fa5bf4","name":"https://git.kernel.org/stable/c/8dc5d98a16fa23c00999aecf10018c9f69fa5bf4","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-98158","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98158","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6722e78c90054101e6797d5944cdc81af9897a0a d0fc3dabfe67caf084e7119ceb2ee23f5ad2f2da git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6722e78c90054101e6797d5944cdc81af9897a0a 0c53eb14975f029abd6b26896a460f0d2aaefe6b git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6722e78c90054101e6797d5944cdc81af9897a0a 717137221c7d90e7c98bda9a370c9da6cbf015e5 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 6722e78c90054101e6797d5944cdc81af9897a0a 8dc5d98a16fa23c00999aecf10018c9f69fa5bf4 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 2.6.15","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 2.6.15 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.111 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.53 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2.7 7.2.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.3-rc3 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["drivers/net/ppp/ppp_async.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"d0fc3dabfe67caf084e7119ceb2ee23f5ad2f2da","status":"affected","version":"6722e78c90054101e6797d5944cdc81af9897a0a","versionType":"git"},{"lessThan":"0c53eb14975f029abd6b26896a460f0d2aaefe6b","status":"affected","version":"6722e78c90054101e6797d5944cdc81af9897a0a","versionType":"git"},{"lessThan":"717137221c7d90e7c98bda9a370c9da6cbf015e5","status":"affected","version":"6722e78c90054101e6797d5944cdc81af9897a0a","versionType":"git"},{"lessThan":"8dc5d98a16fa23c00999aecf10018c9f69fa5bf4","status":"affected","version":"6722e78c90054101e6797d5944cdc81af9897a0a","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["drivers/net/ppp/ppp_async.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"2.6.15"},{"lessThan":"2.6.15","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.111","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.53","versionType":"semver"},{"lessThanOrEqual":"7.2.*","status":"unaffected","version":"7.2.7","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.3-rc3","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.111","versionStartIncluding":"2.6.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.53","versionStartIncluding":"2.6.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2.7","versionStartIncluding":"2.6.15","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.3-rc3","versionStartIncluding":"2.6.15","vulnerable":true}],"negate":false,"operator":"OR"}]}],"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nppp_async: drop the errored frame instead of resetting its headroom\n\nppp_receive_nonmp_frame() prepends a two-byte direction tag before running\nthe pass/active BPF filters:\n\n\t*(__be16 *)skb_push(skb, 2) = htons(PPP_FILTER_INBOUND_TAG);\n\nNothing on the receive path guarantees those two bytes of headroom. The\nframe-error path in ppp_async's process_input_packet() resets a reused skb's\nheadroom to zero while claiming to restore it to a freshly allocated state -\nbut a fresh skb from dev_alloc_skb() carries NET_SKB_PAD:\n\n\terr:\n\t\tif (skb) {\n\t\t\t/* make skb appear as freshly allocated */\n\t\t\tskb_trim(skb, 0);\n\t\t\tskb_reserve(skb, - skb_headroom(skb));\n\t\t}\n\nap->rpkt still points at that skb, so the next frame is reassembled into it\nwith no headroom at all. A peer that sends a bad-FCS frame followed by one\nbeginning ff 03 then leaves a single byte of headroom by the time the filter\ntag is pushed, which lands one byte below skb->head:\n\n  skbuff: skb_under_panic: len:49 put:2 head:ffff888003c10000\n          data:ffff888003c0ffff tail:0x30 end:0x640 dev:<NULL>\n  kernel BUG at net/core/skbuff.c:214!\n  RIP: 0010:skb_panic+0x13e/0x230\n  Call Trace:\n   skb_push+0xbd/0x100\n   ppp_receive_nonmp_frame+0x48a/0x1d10\n   ppp_input+0x4e9/0x2f80\n   ppp_async_process+0x2a/0xe0\n   tasklet_action_common+0x20f/0x8a0\n   handle_softirqs+0x18e/0x590\n  Kernel panic - not syncing: Fatal exception in interrupt\n\nZeroing the headroom violates the NET_SKB_PAD guarantee that dev_alloc_skb()\ngives the rest of the receive path. Besides the filter panic above, when CCP\ncompression is enabled ppp_decompress_frame() hands skb->data - 2 to\n->decompress()/->incomp(), which then reads out of bounds before skb->head\nfor the same reason.\n\nRather than restore the headroom, drop the errored frame - as ppp_synctty\nalready does on its error path - and clear ap->rpkt so the next frame is\nreassembled into a fresh skb with proper headroom. This is simpler and fixes\nboth the filter under-panic and the CCP out-of-bounds read.\n\nThe original V1 of this patch made room in ppp_receive_nonmp_frame() with\nskb_cow_head(); Eric pointed out that fixing the root cause in the transport\nis the right approach.\n\nFound by fuzzing the PPP receive path with a mutating peer on a pty; it is an\ninteresting (remote) DoS: root configures PPP, the peer supplies two crashing\nframes. The reproducer (repro-ppp-skb.c, unchanged from v1) panics in about a\nsecond, and returns cleanly with this applied."}],"providerMetadata":{"dateUpdated":"2026-09-25T10:36:27.608Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/d0fc3dabfe67caf084e7119ceb2ee23f5ad2f2da"},{"url":"https://git.kernel.org/stable/c/0c53eb14975f029abd6b26896a460f0d2aaefe6b"},{"url":"https://git.kernel.org/stable/c/717137221c7d90e7c98bda9a370c9da6cbf015e5"},{"url":"https://git.kernel.org/stable/c/8dc5d98a16fa23c00999aecf10018c9f69fa5bf4"}],"title":"ppp_async: drop the errored frame instead of resetting its headroom","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-98158","datePublished":"2026-09-25T10:36:27.608Z","dateReserved":"2026-09-25T10:25:14.321Z","dateUpdated":"2026-09-25T10:36:27.608Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-25 11:17:47","lastModifiedDate":"2026-09-25 11:17:47","problem_types":[],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"98158","Ordinal":"1","Title":"ppp_async: drop the errored frame instead of resetting its headr","CVE":"CVE-2026-98158","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"98158","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\nppp_async: drop the errored frame instead of resetting its headroom\n\nppp_receive_nonmp_frame() prepends a two-byte direction tag before running\nthe pass/active BPF filters:\n\n\t*(__be16 *)skb_push(skb, 2) = htons(PPP_FILTER_INBOUND_TAG);\n\nNothing on the receive path guarantees those two bytes of headroom. The\nframe-error path in ppp_async's process_input_packet() resets a reused skb's\nheadroom to zero while claiming to restore it to a freshly allocated state -\nbut a fresh skb from dev_alloc_skb() carries NET_SKB_PAD:\n\n\terr:\n\t\tif (skb) {\n\t\t\t/* make skb appear as freshly allocated */\n\t\t\tskb_trim(skb, 0);\n\t\t\tskb_reserve(skb, - skb_headroom(skb));\n\t\t}\n\nap->rpkt still points at that skb, so the next frame is reassembled into it\nwith no headroom at all. A peer that sends a bad-FCS frame followed by one\nbeginning ff 03 then leaves a single byte of headroom by the time the filter\ntag is pushed, which lands one byte below skb->head:\n\n  skbuff: skb_under_panic: len:49 put:2 head:ffff888003c10000\n          data:ffff888003c0ffff tail:0x30 end:0x640 dev:<NULL>\n  kernel BUG at net/core/skbuff.c:214!\n  RIP: 0010:skb_panic+0x13e/0x230\n  Call Trace:\n   skb_push+0xbd/0x100\n   ppp_receive_nonmp_frame+0x48a/0x1d10\n   ppp_input+0x4e9/0x2f80\n   ppp_async_process+0x2a/0xe0\n   tasklet_action_common+0x20f/0x8a0\n   handle_softirqs+0x18e/0x590\n  Kernel panic - not syncing: Fatal exception in interrupt\n\nZeroing the headroom violates the NET_SKB_PAD guarantee that dev_alloc_skb()\ngives the rest of the receive path. Besides the filter panic above, when CCP\ncompression is enabled ppp_decompress_frame() hands skb->data - 2 to\n->decompress()/->incomp(), which then reads out of bounds before skb->head\nfor the same reason.\n\nRather than restore the headroom, drop the errored frame - as ppp_synctty\nalready does on its error path - and clear ap->rpkt so the next frame is\nreassembled into a fresh skb with proper headroom. This is simpler and fixes\nboth the filter under-panic and the CCP out-of-bounds read.\n\nThe original V1 of this patch made room in ppp_receive_nonmp_frame() with\nskb_cow_head(); Eric pointed out that fixing the root cause in the transport\nis the right approach.\n\nFound by fuzzing the PPP receive path with a mutating peer on a pty; it is an\ninteresting (remote) DoS: root configures PPP, the peer supplies two crashing\nframes. The reproducer (repro-ppp-skb.c, unchanged from v1) panics in about a\nsecond, and returns cleanly with this applied.","Type":"Description","Title":"ppp_async: drop the errored frame instead of resetting its headr"}]}}}