From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BF26C3F1059 for ; Sat, 29 Aug 2026 06:39:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787985590; cv=none; b=PRoV/uzNWTRqgHR1TrZn54R6fLPHdX0cvIdMY1lnTj3d0XzVW4hIWXTdCYJcwFwXBZWumdsMiiUkKs6FeYXS9XHYna5lxm63Z5YnA7K1tnpJEouN3c2oJefUvMHOsYD0J9T4PoaqktIw8KTXGbKX2tHkTcOEz9ETheUwzQf0Sk8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787985590; c=relaxed/simple; bh=gCfStg91E1lIxEzS80z3+/s7yT036OApKrdWclNbCtQ=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=hXgYMkngh7i0opSzs32bl1D6nW2BcM776+rZ4vdSXk6ZiarLbDOGjuLWqKi86JW859lsWZSFItqP9+STjdKptRpppUeiNLbPN9W2WLbpeqoVbZ/fOqCtlziob7MYMy5ui8z9S5pGvGbqk42MAd6u3d0PCXyG93uJ3OOctNN/2A8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=rJ41UcGk; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="rJ41UcGk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BD0951F000E9; Sat, 29 Aug 2026 06:39:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787985589; bh=vqVq6IrBcKHfdfjP+ijgqaVabxVrR5rXWPd3KTc3NiE=; h=From:To:Cc:Subject:Date:Reply-To; b=rJ41UcGkElJU+3W/2RxWkYINCEBfkUy3wgPKbbkC7b+71wjVamCokAwe4ZM/eW0S6 27iQONDFn9MKc2tbE3JAQNSHYlU5OAz9KoY0XjzEpG8Qyuqh5Vg/QDouegqdOf46g7 vukLZPBTXhNTZySpiPvg+7CHJnvqw3jXyg1HTiTc= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-80725: net: gro: properly validate BIG TCP aggregation criteria Date: Sat, 29 Aug 2026 08:37:59 +0200 Message-ID: <2026082958-CVE-2026-80725-da71@gregkh> X-Mailer: git-send-email 2.55.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3329; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=0JEWHonHEdfr0grgH5nUIoHM4Mroolu8vVBR14AtEPU=; b=owGbwMvMwCRo6H6F97bub03G02pJDFmT6tx87WPXir8LmeYi1OWzOvT16Uu3Lwcxve05Eccx5 17VfaUnHbEsDIJMDLJiiixftvEc3V9xSNHL0PY0zBxWJpAhDFycAjCRiuUMCy41vvV61fTMbMon 1bU7fENtvFhyTjDMM8zP59mzU4upuPjIxc6jh0yFFHcbAwA= X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: net: gro: properly validate BIG TCP aggregation criteria When GRO attempts to aggregate packets beyond GRO_LEGACY_MAX_SIZE (64KB), BIG TCP should only be permitted for plain IPv4 TCP and plain IPv6 TCP (with sufficient MAC header room to insert the temporary HBH jumbo header). However, commit b1a78b9b9886 ("net: add support for ipv4 big tcp") loosened the check in skb_gro_receive(), leading to several issues: 1. skb_gro_receive() checked skb_headroom(p) instead of the actual space before the MAC header (p->mac_header). Because skb_headroom(p) includes mac_len, crafted frames (e.g. injected via AF_PACKET) can pass the check with p->mac_header < 8 bytes. When ipv6_gro_complete() inserts the temporary HBH jumbo header, the memmove() starts before skb->head, causing an out-of-bounds write and wrapping skb->mac_header. 2. It allowed non-IP protocols such as software VLAN (ETH_P_8021Q / ETH_P_8021AD) to aggregate beyond 64KB because p->protocol != ETH_P_IPV6 was true. 3. It checked p->encapsulation instead of NAPI_GRO_CB(skb)->encap_mark, allowing encapsulated flows (e.g. SIT / IPv6-in-IPv4) to aggregate beyond 64KB. Fix skb_gro_receive() to strictly enforce: - NAPI_GRO_CB(skb)->proto == IPPROTO_TCP - Not encapsulated (!NAPI_GRO_CB(skb)->encap_mark && !p->encapsulation) - Protocol must be either ETH_P_IP or ETH_P_IPV6 - If ETH_P_IPV6, p->mac_header must be at least sizeof(struct hop_jumbo_hdr) Returning -E2BIG from skb_gro_receive() ensures that packets which cannot become BIG TCP are cleanly flushed at <= 64KB and delivered intact without dropping. This issue does not exist in mainline (7.0+) because the subsystem was rewritten in commit 81be30c1f5f2 ("net/ipv6: Drop HBH for BIG TCP on RX side"), making this fix relevant only for older stable branches like 6.18.y. The Linux kernel CVE team has assigned CVE-2026-80725 to this issue. Affected and fixed versions =========================== Issue introduced in 5.19 with commit 0fe79f28bfaf73b66b7b1562d2468f94aa03bd12 and fixed in 6.18.47 with commit 3ce832e2bd431d0c12ba525ed73ad8fbc4191da5 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2026-80725 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: net/core/gro.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/3ce832e2bd431d0c12ba525ed73ad8fbc4191da5