SUNRPC: Reject krb5 v2 wrap tokens with oversized ec field
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 blo
CVE-2026-89538
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-89538
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "cf4c024b908353fcc48309374d39e3399d67dfd1",
"lessThan": "ac9efc29346b6942e71f0e24a3178a9121330fab",
"versionType": "git"
},
{
"status": "affected",
"version": "cf4c024b908353fcc48309374d39e3399d67dfd1",
"lessThan": "b5746095b59f4d11f39f08751d36bbdfd1e5deac",
"versionType": "git"
},
{
"status": "affected",
"version": "cf4c024b908353fcc48309374d39e3399d67dfd1",
"lessThan": "9fc6d6e6db49ab55208d5dd1c424c1d0d9aa7296",
"versionType": "git"
},
{
"status": "affected",
"version": "cf4c024b908353fcc48309374d39e3399d67dfd1",
"lessThan": "4abb44a29bb515df6f49123848765c70fc9b5021",
"versionType": "git"
},
{
"status": "affected",
"version": "cf4c024b908353fcc48309374d39e3399d67dfd1",
"lessThan": "dfcd81ab45613d45996fbf483d4ef54b0ec90ab9",
"versionType": "git"
},
{
"status": "affected",
"version": "cf4c024b908353fcc48309374d39e3399d67dfd1",
"lessThan": "1f9856af065b6158271687e9788407b9573fd16f",
"versionType": "git"
},
{
"status": "affected",
"version": "cf4c024b908353fcc48309374d39e3399d67dfd1",
"lessThan": "880effc943ed82d6811f272ed3307c222b40f4d6",
"versionType": "git"
},
{
"status": "affected",
"version": "cf4c024b908353fcc48309374d39e3399d67dfd1",
"lessThan": "ad484748eec0a66eac0f13ab53b3fbedb7333c91",
"versionType": "git"
}
],
"programFiles": [
"net/sunrpc/auth_gss/gss_krb5_wrap.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "3.13"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "3.13",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.270",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.221",
"versionType": "semver",
"lessThanOrEqual": "5.15.*"
},
{
"status": "unaffected",
"version": "6.1.188",
"versionType": "semver",
"lessThanOrEqual": "6.1.*"
},
{
"status": "unaffected",
"version": "6.6.157",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.109",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.50",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.4",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/sunrpc/auth_gss/gss_krb5_wrap.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-89538
Source reference:
/cveMetadata/cveId
Publisher severity
critical
Source reference: /containers/cna/metrics
- Event
- #35057 · Revision 1
- Added to Heist Feed
- Publisher date