{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89538", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.721Z", "datePublished": "2026-09-11T19:44:15.953Z", "dateUpdated": "2026-10-19T08:48:29.976Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:48:29.976Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nSUNRPC: Reject krb5 v2 wrap tokens with oversized ec field\n\ngss_krb5_unwrap_v2() sets buf->len to a logical\nlength, which can be much smaller than head[0].iov_len\n(the allocated receive-page capacity). It then calls\nxdr_buf_trim() with a trim length derived from the 16-bit\n\"extra count\" (ec) field in the Kerberos v2 token header.\n\nThe ec field is authenticated by the post-decrypt memcmp()\nagainst the encrypted header copy, so a randomly-mutated\nvalue is rejected. However, any peer holding a valid GSS\ncontext can legitimately encrypt a token whose ec exceeds\nthe plaintext length. Per RFC 4121, such a token is\nstructurally malformed.\n\nAlthough xdr_buf_trim() now clamps the buf->len subtraction\nto avoid unsigned underflow, the buffer is still left in a\nsemantically invalid state (zero length, inconsistent iov\nlengths) when ec is oversized.\n\nReject these tokens before calling xdr_buf_trim(), giving\ncallers a well-defined GSS_S_DEFECTIVE_TOKEN error and\nkeeping the xdr_buf internally consistent. The wrapped blob\nbegins at a nonzero offset -- both callers pass len as\noffset + opaque_len -- so buf->len still counts the offset\nbytes that precede the blob. Compare the trim length\nagainst the remaining wrapped segment, buf->len - offset,\nrather than the whole buffer; comparing against buf->len\nalone leaves an offset-wide window in which an oversized ec\npasses the test and xdr_buf_trim() cuts into the bytes ahead\nof the blob." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL" }, "scenarios": [ { "lang": "en", "value": "AV:N - gss_krb5_unwrap_v2() is reached from nfsd RPCSEC_GSS privacy unwrap on TCP/2049 and from the NFS client's gss_unwrap_resp_priv() on every krb5p reply, so a remote NFS peer delivers the oversized-ec wrap token over the network.\nAC:L - A peer holding the GSS session keys can encrypt a RFC 4121 wrap token whose authenticated ec exceeds the plaintext; decrypt and the header memcmp succeed, then xdr_buf_trim() runs with that chosen length and no race or layout outside attacker control.\nPR:N - A malicious or compromised NFS server that already shares a krb5p GSS context needs no account or capability on the victim client; ordinary krb5p replies and NFSv4.0 GSS callbacks are processed without local privileges on that host.\nUI:N - Once a krb5p NFS mount exists, the client unwraps every privacy-protected reply and NFSv4.0 GSS callback with no further mount, click, or open; idle revalidations and server-driven callbacks are sufficient.\nS:U - The corrupted xdr_buf and subsequent XDR decode and shift run in the host kernel that processed the RPC and do not cross a VM, IOMMU, or sandbox boundary.\nC:H - An oversized ec makes xdr_buf_trim() underflow buf->len toward UINT_MAX, so later xdr_read_pages/xdr_shrink_bufhead use that length as a copy bound and read far past the receive buffer into adjacent kernel memory.\nI:H - xdr_shrink_bufhead() then calls xdr_buf_head_shift_right() with a near-UINT_MAX length derived from the wrapped buf->len, an out-of-bounds write into kernel memory that can be used for control-flow hijacking.\nA:H - Those unbounded XDR copies and the inconsistent xdr_buf (wrapped or zero length versus iov_lens) oops or panic nfsd or the NFS client, and the peer can repeat the request at will." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/sunrpc/auth_gss/gss_krb5_wrap.c" ], "versions": [ { "version": "cf4c024b908353fcc48309374d39e3399d67dfd1", "lessThan": "ac9efc29346b6942e71f0e24a3178a9121330fab", "status": "affected", "versionType": "git" }, { "version": "cf4c024b908353fcc48309374d39e3399d67dfd1", "lessThan": "b5746095b59f4d11f39f08751d36bbdfd1e5deac", "status": "affected", "versionType": "git" }, { "version": "cf4c024b908353fcc48309374d39e3399d67dfd1", "lessThan": "9fc6d6e6db49ab55208d5dd1c424c1d0d9aa7296", "status": "affected", "versionType": "git" }, { "version": "cf4c024b908353fcc48309374d39e3399d67dfd1", "lessThan": "4abb44a29bb515df6f49123848765c70fc9b5021", "status": "affected", "versionType": "git" }, { "version": "cf4c024b908353fcc48309374d39e3399d67dfd1", "lessThan": "dfcd81ab45613d45996fbf483d4ef54b0ec90ab9", "status": "affected", "versionType": "git" }, { "version": "cf4c024b908353fcc48309374d39e3399d67dfd1", "lessThan": "1f9856af065b6158271687e9788407b9573fd16f", "status": "affected", "versionType": "git" }, { "version": "cf4c024b908353fcc48309374d39e3399d67dfd1", "lessThan": "880effc943ed82d6811f272ed3307c222b40f4d6", "status": "affected", "versionType": "git" }, { "version": "cf4c024b908353fcc48309374d39e3399d67dfd1", "lessThan": "ad484748eec0a66eac0f13ab53b3fbedb7333c91", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/sunrpc/auth_gss/gss_krb5_wrap.c" ], "versions": [ { "version": "3.13", "status": "affected" }, { "version": "0", "lessThan": "3.13", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.270", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.221", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.188", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.157", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.109", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.50", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.4", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.13", "versionEndExcluding": "5.10.270" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.13", "versionEndExcluding": "5.15.221" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.13", "versionEndExcluding": "6.1.188" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.13", "versionEndExcluding": "6.6.157" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.13", "versionEndExcluding": "6.12.109" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.13", "versionEndExcluding": "6.18.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.13", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.13", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/ac9efc29346b6942e71f0e24a3178a9121330fab" }, { "url": "https://git.kernel.org/stable/c/b5746095b59f4d11f39f08751d36bbdfd1e5deac" }, { "url": "https://git.kernel.org/stable/c/9fc6d6e6db49ab55208d5dd1c424c1d0d9aa7296" }, { "url": "https://git.kernel.org/stable/c/4abb44a29bb515df6f49123848765c70fc9b5021" }, { "url": "https://git.kernel.org/stable/c/dfcd81ab45613d45996fbf483d4ef54b0ec90ab9" }, { "url": "https://git.kernel.org/stable/c/1f9856af065b6158271687e9788407b9573fd16f" }, { "url": "https://git.kernel.org/stable/c/880effc943ed82d6811f272ed3307c222b40f4d6" }, { "url": "https://git.kernel.org/stable/c/ad484748eec0a66eac0f13ab53b3fbedb7333c91" } ], "title": "SUNRPC: Reject krb5 v2 wrap tokens with oversized ec field", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2026-89538", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "yes" }, { "Technical Impact": "total" } ], "version": "2.0.3", "timestamp": "2026-10-16T19:23:19.852732Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:26:41.901Z" } } ] } }