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 D06AD568531 for ; Fri, 11 Sep 2026 19:55:01 +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=1789156506; cv=none; b=H78DkBFH7qym+4w9UUgxk8IFwnh27JBaNY93un8UinK2xykjyKr90F1NH8Z7Qq3lQhGObLWp1ZTPHK0Tpj1Mrn+LAy6BgPWS9zjkMBqiKAsoKKPXlLCd0Ye9EUcvfTZ82NnEn7THkoECALMBGfKnTeCrMxbHfz6HA2LcL18//4I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789156506; c=relaxed/simple; bh=L68TCIU6fP42veK5CBpNX/+CXpWwZ+9FH0mKLcA9AvA=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=htoOnN+TNdHsms0rUqlpGS4k++MnnaoFIzSSszxR23z2mbSVAiz6dZSrsC7cvJ4dmoLF2Idh1XEsW867kk6RbFXtqlIbl2Vm59FZ3659KzHftWGFWoRalr6vFV93yRaY2wtI+xz0JfP5eeYjUTpB5WdOGBPb7KdV5AgIw3Ia/ss= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Unq2Up8z; 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="Unq2Up8z" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1F9F41F00899; Fri, 11 Sep 2026 19:54:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789156500; bh=+42AIuoXif8CSQz7JJKbC7WyEqsnV9pDvTXwD4izA00=; h=From:To:Cc:Subject:Date:Reply-To; b=Unq2Up8zIeWQbeiAccb+xk67ZiRn8MaHQGuSg4I/6eY9d9AMMr9434PdSD2BFqmBt 06V7856KkhqsR92KEKsU2W5v5FR5aTv8tQ4CqiWuJCQH6GdI9nSX/+IHV0PDJjGxNw jS27tVA00S7klEKgaxl1KUIaubIhDxAAd/y2Hxwg= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-89538: SUNRPC: Reject krb5 v2 wrap tokens with oversized ec field Date: Fri, 11 Sep 2026 21:43:47 +0200 Message-ID: <2026091118-CVE-2026-89538-c58d@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=3649; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=R3rMlDLpNt+86dh/pCizrM81Fjd5t9dy0NgwAZlK/I4=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlLIuPaBeM57j45KBVb78y9gyNzoRzbg0X7F+9QrwtZ9 bB76e8/HbEsDIJMDLJiiixftvEc3V9xSNHL0PY0zBxWJpAhDFycAjCRjvkMMxkb/63kyZn82n65 1qXdX+99XfH2WSrD/PTZrqeunK4zfpj4dfNdl9PCMb26/gA= 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: SUNRPC: Reject krb5 v2 wrap tokens with oversized ec field gss_krb5_unwrap_v2() sets buf->len to a logical length, which can be much smaller than head[0].iov_len (the allocated receive-page capacity). It then calls xdr_buf_trim() with a trim length derived from the 16-bit "extra count" (ec) field in the Kerberos v2 token header. The ec field is authenticated by the post-decrypt memcmp() against the encrypted header copy, so a randomly-mutated value is rejected. However, any peer holding a valid GSS context can legitimately encrypt a token whose ec exceeds the plaintext length. Per RFC 4121, such a token is structurally malformed. Although xdr_buf_trim() now clamps the buf->len subtraction to avoid unsigned underflow, the buffer is still left in a semantically invalid state (zero length, inconsistent iov lengths) when ec is oversized. Reject these tokens before calling xdr_buf_trim(), giving callers a well-defined GSS_S_DEFECTIVE_TOKEN error and keeping the xdr_buf internally consistent. The wrapped blob begins at a nonzero offset -- both callers pass len as offset + opaque_len -- so buf->len still counts the offset bytes that precede the blob. Compare the trim length against the remaining wrapped segment, buf->len - offset, rather than the whole buffer; comparing against buf->len alone leaves an offset-wide window in which an oversized ec passes the test and xdr_buf_trim() cuts into the bytes ahead of the blob. The Linux kernel CVE team has assigned CVE-2026-89538 to this issue. Affected and fixed versions =========================== Issue introduced in 3.13 with commit cf4c024b908353fcc48309374d39e3399d67dfd1 and fixed in 6.12.109 with commit dfcd81ab45613d45996fbf483d4ef54b0ec90ab9 Issue introduced in 3.13 with commit cf4c024b908353fcc48309374d39e3399d67dfd1 and fixed in 6.18.50 with commit 1f9856af065b6158271687e9788407b9573fd16f Issue introduced in 3.13 with commit cf4c024b908353fcc48309374d39e3399d67dfd1 and fixed in 7.2.4 with commit 880effc943ed82d6811f272ed3307c222b40f4d6 Issue introduced in 3.13 with commit cf4c024b908353fcc48309374d39e3399d67dfd1 and fixed in 7.3-rc1 with commit ad484748eec0a66eac0f13ab53b3fbedb7333c91 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-2026-89538 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/sunrpc/auth_gss/gss_krb5_wrap.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/dfcd81ab45613d45996fbf483d4ef54b0ec90ab9 https://git.kernel.org/stable/c/1f9856af065b6158271687e9788407b9573fd16f https://git.kernel.org/stable/c/880effc943ed82d6811f272ed3307c222b40f4d6 https://git.kernel.org/stable/c/ad484748eec0a66eac0f13ab53b3fbedb7333c91